Inertia is the tendency of objects to keep moving in a straight line at constant linear velocity. The principle of inertia is used to describe the motion of objects and how they are affected by applied forces. The inate force of matter, is a power of resisting by which every body endeavours to preserve its present state, whether it be of rest or of moving uniformly forward in a straight line. An object not subject to any external force moves at a constant velocity. Thus, an object will continue moving at its current velocity until some force causes its speed or direction to change.
to attribute human form or personality to things not human.
Binary Structure of Abstract Connector. The overt matrix Ko of the abstract connector K forms a closed system in sharp contradistinction to the covert matrix Kc of the same connector, which forms an open set. In simpler words, the overt part of it is only 'the tip of the iceberg'. But the Ko/Kc correlation in prospective structures (it must be emphasized that the picture in retrospective structures is quite different) functions as a 'data bank' for the actual linearization of the S-S' axis of manifestation. The open-ended Sz propositional content of Kc is contrasted with the conventionally featurizable content features of discourse structure'). There are two fundamental relations between the abstract connector and the linear manifestation: (a) one-to-many; (b) many-to-one. The former is usually and conventionally handled under ambiguity, whereas the latter is essentially reducible to the paraphrase relation. The balance between Ko and Kc is the actual trigger of alternative realizations of one and the same semantic interpretation. The overt matrices contain, among others, indicators of discourse head compatibility, markers of deixis (time, place, and person), and diagrammed accounts of the semantic substance of conventional and non-conventional conjoiners.

Any hypermorpheme, taken in isolation, evinces (a) asserted meaning, and (b) presupposed meaning. Any given set of linearized hypermorphemes evinces in addition 'connective' meaning, derived from hypermorphemic juxtaposition, and reflected in either or both of the twin matrices of abstract connectors. However, it must be pointed out that these abstract connectors are no mere inventories of realizations; they should rather be viewed as ranges of potentials -- some being realized overtly, others covertly, and still others not being realized at all. But the model is pragmatics-oriented: the direct outcome of this is that production matrices never coincide completely with reception matrices. This is indeed one of the major sources of misreading, deliberate or unintentional miscomprehension, semi-intelligibility, etc.
Mapping Discourse Structure
I draw
you draw
he/she/it draws
we draw
you draw
they draw

Present continuous
I am drawing
you are drawing
he/she/it is drawing
we are drawing
you are drawing
they are drawing

Simple past
I drew
you drew
he/she/it drew
we drew
you drew
they drew

Past continuous
I was drawing
you were drawing
he/she/it was drawing
we were drawing
you were drawing
they were drawing

Present perfect
I have drawn
you have drawn
he/she/it has drawn
we have drawn
you have drawn
they have drawn

Present perfect continuous
I have been drawing
you have been drawing
he/she/it has been drawing
we have been drawing
you have been drawing
they have been drawing

Past perfect
I had drawn
you had drawn
he/she/it had drawn
we had drawn
you had drawn
they had drawn

Past perfect continuous
I had been drawing
you had been drawing
he/she/it had been drawing
we had been drawing
you had been drawing
they had been drawing

I will draw
you will draw
he/she/it will draw
we will draw
you will draw
they will draw

Future continuous
I will be drawing
you will be drawing
he/she/it will be drawing
we will be drawing
you will be drawing
they will be drawing

Future perfect
I will have drawn
you will have drawn
he/she/it will have drawn
we will have drawn
you will have drawn
they will have drawn

Future perfect continuous
I will have been drawing
you will have been drawing
he/she/it will have been drawing
we will have been drawing
you will have been drawing
they will have been drawing

Conditional present
I would draw
you would draw
he/she/it would draw
we would draw
you would draw
they would draw

Conditional perfect
I would have drawn
you would have drawn
he/she/it would have drawn
we would have drawn
you would have drawn
they would have drawn

Conditional present progressive
I would be drawing
you would be drawing
he/she/it would be drawing
we would be drawing
you would be drawing
they would be drawing

Conditional perfect progressive
I would have been drawing
you would have been drawing
he/she/it would have been drawing
we would have been drawing
you would have been drawing
they would have been drawing

Present subjunctive
I draw
you draw
he/she/it draw
we draw
you draw
they draw

Past subjunctive
I drew
you drew
he/she/it drew
we drew
you drew
they drew

Past perfect subjunctive
I had drawn
you had drawn
he/she/it had drawn
we had drawn
you had drawn
they had drawn

Future subjunctive

you draw
we Let´s draw
you draw

Present participle

Past participle
Bérard has shown in careful analysis of individual passages that Homer, in true Greek fashion, anthropomorphized facts, making what was informative, but unexciting, into the liveliest of realities.
Danish: Gjentagelsen
Glossary of chess

Absolute pin
A pin against the king is called absolute since the pinned piece cannot legally move (as moving it would expose the king to check). Cf. relative pin.

1. Describes a piece that controls a number of squares, or a piece that has a number of squares available for its next move.
2. An "active defense" is a defense employing threat(s) or counterattack(s).
Antonym: passive.
Envelope used for the adjournment of a match game Efim Geller vs. Bent Larsen, Copenhagen 1966

Suspension of a chess game with the intention to finish it later. It was once very common in high-level competition, often occurring soon after the first time control, but the practice has been abandoned due to the advent of computer analysis. See sealed move.
Decision by a strong chess player (the adjudicator) on the outcome of an unfinished game. This practice is now uncommon in over-the-board events, but does happen in online chess when one player refuses to continue after an adjournment.

Adjust (see Touch-move rule)
To adjust the position of a piece on its square without being required to move it. A player may only do this on his turn to move, and he must first say "I adjust", or the French equivalent "J'adoube".

Advanced pawn
A pawn that is on the opponent's side of the board (the fifth rank or higher). An advanced pawn may be weak if it is overextended, lacking support and difficult to defend, or strong if it cramps the enemy by limiting mobility. An advanced passed pawn that threatens to promote can be especially strong.

A better position with the chance of winning the game. Evaluation factors can include space, time, material, and threats.
[see Alekhine vs. Nimzowitsch, 1930]

Alekhine's gun
A formation in which a queen backs up two rooks on the same file.

Algebraic notation
The standard way to record the moves of a chess game, using alphanumeric coordinates for the squares.

The distinction between professional and amateur is not very important in chess as amateurs may win prizes, accept appearance fees, and earn any title, including World Champion. In the 19th century, "Amateur" was sometimes used in published game scores to conceal the name of the losing player in a Master vs. Amateur contest. It was thought to be impolite to use a player's name without permission, and the professional did not want to risk losing a customer. See also NN or N.N.

The study of a position to determine best play for both sides.

Written commentary on a game using a combination of comments, chess symbols and/or notation.

Announced mate
A practice, common in the 19th century, whereby a player would announce a sequence of moves, believed by him to constitute best play by both sides, that led to a forced checkmate for the announcing player in a specified number of moves (for example, "mate in five").

A move or a plan that is not in accordance with the principles of positional play. Antipositional is used to describe moves that are part of an incorrect plan rather than a mistake made when trying to follow a correct plan. Antipositional moves are often pawn moves; since pawns cannot move backwards to return to squares they have left, their advance often creates irreparable weaknesses.

An opening variation that White uses against the Sicilian Defense (1.e4 c5) other than the most common plan of 2.Nf3 followed by 3.d4 cxd4 4.Nxd4 (the Open Sicilian). Some Anti-Sicilians include the Alapin Variation (2.c3), Moscow Variation (2.Nf3 d6 3.Bb5+), Rossolimo Variation (2.Nf3 Nc6 3.Bb5), Grand Prix Attack (2.Nc3 Nc6 3.f4 g6 4.Nf3 Bg7 and now 5.Bc4 or 5.Bb5), Closed Sicilian (2.Nc3 followed by g3 and Bg2), Smith–Morra Gambit (2.d4 cxd4 3.c3), and Wing Gambit (2.b4).
See International Arbiter.

Armageddon chess
A game which, under the tournament rules, counts as a win for Black if it ends in a draw. Typically the tournament rules allow White more time than Black in such games: the discrepancy can vary; usually in FIDE World Championships, White has six minutes, while Black only has five, but in the World Chess Championship 2012 the following time control was used: 5 minutes for White, 4 minutes for Black; plus 3 seconds increment per move from move 60. This format is typically used in playoff tie-breakers when shorter blitz games have not resolved the tie.

artificial castling
Refers to a maneuver of several separate moves by the king and by a rook where they end up as if they had castled. Also known as castling by hand.
An assault, either short-term (e.g., after 1.e4 Nf6, Black is attacking White's pawn on e4) or long-term, for example in the form of a sustained mating attack against the enemy king or a minority attack against the opponent's queenside pawn structure. See defence.
The sacrifice of minor or major pieces to expose the enemy king. For example, if the black king has castled and is on the g8-square, White may attempt to attract the king by using forcing moves such as Bxh7+, followed by Ng5+ etc. See decoy.
A self-operating chess-playing machine. Popular attractions in the 18th and 19th centuries, these devices were hoaxes under the control of a human player. The most famous chess-playing "automaton" was The Turk.

Symbol used for the bishop when recording chess moves in English.
back rank
A player's first rank (the one on which the pieces stand in the starting position); White's back rank is Black's eighth rank, and vice versa.

back-rank mate
A checkmate delivered by a rook or queen along a back rank from which the mated king is unable to move because it is blocked by friendly pieces (usually pawns) on the second rank. This is also sometimes referred to as a back-row mate.

back-rank weakness
A situation in which a player is under threat of a back-rank mate and, having no time/option to create an escape for the king, must constantly watch and defend against that threat, for example by keeping a rook on the back rank.

backward pawn
A pawn that is behind a pawn of the same color on an adjacent file and that cannot be advanced with the support of another pawn.

bad bishop
A bishop that is hemmed in by the player's own pawns. See also good bishop.

bare king
A position in which a king is the only man of its color on the board.

An arrangement of two pieces in line with the enemy king on a rank, file, or diagonal so that if the middle piece moves a discovered check will be delivered. The term is also used in cases where moving the middle piece will uncover a threat along the opened line other than a check.

British Chess Federation, the former name of the English Chess Federation. See ECF.

An abbreviation for the British Chess Magazine.

An abbreviation for the 1982 openings reference book Batsford Chess Openings, by Raymond Keene and Garry Kasparov. The second edition (1989) is often called BCO-2. Cf. ECO and MCO.

A strong grip or stranglehold on a position that is difficult for the opponent to break. A bind is usually an advantage in space created by advanced pawns. The Maróczy Bind is a well-known example. See also squeeze.

Chess bishop icon.png see bishop

bishop pair
In open positions, two bishops are considered to have an advantage over two knights or a knight and a bishop. (In closed positions knights may be more valuable than bishops.) The player with two bishops is said to have the bishop pair. Some evaluation systems count the bishop pair as worth half a pawn, see Chess piece relative value#Alternate valuations.

bishop pawn
A pawn on the bishop's file, i.e. the c-file or f-file.

bishops on opposite colors (or bishops of opposite colors)
A situation in which one player has only his light-square bishop remaining while the other has only his dark-square bishop remaining. In endgames, this often results in a draw if there are no other pieces (only pawns), even if one side has a material advantage of one, two or even three pawns, since the bishops control different squares (see Opposite-colored bishops endgame). In the middlegame, however, the presence of opposite-colored bishops imbalances the game and can lead to mating attacks, since each bishop attacks squares that cannot be covered by the other.

The dark-colored squares on the chessboard are often referred to as "the black squares" even though they are often some other dark color. Similarly, "the black pieces" are sometimes actually some other (usually dark) color. See also white.

Black (see White and Black in chess)
The designation for the player who moves second, even though his pieces ("the black pieces") are sometimes actually some other (usually dark) color. See also White and first-move advantage.
blind chess
See Kriegspiel.

blindfold chess
A form of chess in which one or both players are not allowed to see the board.

Blitz chess (see Fast chess)
A fast form of chess (from German Blitz, "lightning") with a very short time limit, usually 3 or 5 minutes per player for the entire game. With the advent of electronic chess clocks, the time remaining is often incremented by 1 or 2 seconds per move.
A strategic placement of a minor piece directly in front of an enemy pawn, where it restrains the pawn's advance and gains shelter from attack. Blockading pieces are often overprotected.
A very bad move, an oversight (indicated by "??" in notation).

See chessboard.
Schulder vs. Boden, London 1853


Boden's Mate
Boden's Mate
Boden's Mate, named for Samuel Boden, is a checkmate pattern in which the king, usually having castled queenside, is checkmated by two crisscrossing bishops. Immediately prior to delivering the mate, the winning side typically plays a queen sacrifice on c3 or c6 to set up the mating position.
book draw
An endgame position known to be a draw with perfect play. Historically this was established by reference to chess endgame literature, but in simplified positions (currently six pieces or fewer[citation needed]) computer analysis in an endgame tablebase can be used.
book move
An opening move found in standard reference books on opening theory. A game is said to be "in book" when both players are playing moves found in the opening references. A game is said to be "out of book" when the players have reached the end of the variations analyzed in the opening books, or if one of the players deviates with a novelty (or a blunder).
book win
An endgame position known to be a win with perfect play. Historically this was established by reference to chess endgame literature, but in simplified positions (currently six pieces or fewer[citation needed]) computer analysis in an endgame tablebase can be used.
A pawn advance or capture that opens a blocked position.
Destruction of a seemingly strong defense, often by means of a sacrifice.
[chiefly British] See miniature.
A spectacular and beautiful game of chess, generally featuring sacrificial attacks and unexpected moves. Brilliancies are not always required to feature sound play or the best moves by either side.
brilliancy prize
A prize awarded at some tournaments for the best brilliancy played in the tournament.
Bughouse chess
Bronstein delay
A time control method with time delay, invented by David Bronstein. When it becomes a player's turn to move, the clock waits for the delay period before starting to subtract from the player's remaining time.
Bughouse chess
A popular chess variant played with teams of two or more.
building a bridge
Making a path for a king by providing protective cover against checks from line-pieces. A well-known example is the Lucena position.
Bullet chess (see Fast chess)
A form of chess in which each side has 1 minute to make all their moves.
Colloquial term for a refutation of an opening, or of previously published analysis. A famous example is Bobby Fischer's 1961 article "A Bust to the King's Gambit" in which he wrote, "In my opinion, the King's Gambit is busted. It loses by force."[1]
A tournament round in which a player does not have a game, usually because there are an odd number of players. A bye is normally scored as a win (1 point), although in some tournaments a player is permitted to choose to take a bye (usually in the first or last round) and score it as a draw (½ point).


The goddess of chess, occasionally invoked to indicate luck or good fortune: "Caïssa was with me."
To carefully plan a series of moves while considering possible responses.
candidate move
A move that seems good upon initial observation of the position, and that warrants further analysis.
Candidates Match
A knockout match in the Candidates Tournament.
Candidates Tournament
A tournament organised by the FIDE, the third and last qualifying cycle of the World Chess Championship. The participants are the top players of the Interzonal tournament plus possibly other players selected on the basis of rating or performance in the previous candidates tournament. The top ranking player(s) qualify(ies) for the world championship.
capped piece
A certain piece with which one player tries to deliver checkmate. Agreeing to play with a capped piece provides the stronger player an extra challenge, thereby conferring upon himself a handicap in chess. When the capped piece is a pawn, it is called a pion coiffé [from French: "capped pawn"].
1. [verb] To remove the opponent's man from the board by taking it with one's own man. Except in the case of an en passant capture, the capturing man replaces the captured man on its square.
2. [noun] A move that captures.
A special move involving both the king and one rook. Its purpose is generally to protect the king and develop the rook. Castling on the kingside is sometimes called "castling short" and castling on the queenside is called "castling long"; the difference is based on whether the rook moves a short distance (two squares) or a long distance (three squares).
castling into it
A situation where one side castles and a result is that the king is in more danger at the destination than on the initial square, either immediately or because lines and diagonals can be more readily opened against it. Because beginners often falsely assume castling to always improve protection of the king, the pre-war grandmaster and leading figure of the hypermodern school Richard Réti exhorted players to "castle because you must, not because you can."
castling long
Castling queenside; in chess notation: 0-0-0.
castling short
Castling kingside; in chess notation: 0-0.
casual game
See friendly game.
Category tournament
The category of a tournament is a measure of its strength based on the average FIDE rating of the participants. The category is calculated by rounding up the number: (average rating − 2250) / 25. So each category covers a 25-point rating range, starting with Category 1 which spans ratings between 2251 and 2275. A Category 18 tournament has an average rating between 2676 and 2700.
An abbreviation sometimes used for correspondence chess.
centralisation (or centralization)
Moving a piece or pieces toward the center of the board. In general, pieces are best placed in or near the center of the board because they control a large number of squares and are available for play on either flank as needed. Because of their limited mobility, knights in particular benefit from being centralized. There are several chess aphorisms referring to this principle: "A knight on the rim is dim [or, grim]" and "A knight on the side cannot abide."
central pawn
A pawn on the king's file (e-file) or queen's file (d-file).

The centre squares are marked "×".
centre (or center)
The four squares in the middle of the board.
centre pawn (or center pawn)
See central pawn.
Slang for a primitive trap, often set in the hope of swindling a win or a draw from a lost position.
A direct attack on the king by an enemy man. The attacked king is said to be in check.
A position in which a player's king is in check and the player has no legal move (i.e. cannot move out of or escape the check). A player whose king is checkmated loses the game.
A chess variant with a randomized positioning of the back-rank pieces to start the game. Also known as Fischer Random Chess.
The chequered board used in chess, consisting of 64 squares (eight rows by eight columns) arranged in two alternating colors, light and dark.
A chess clock
chess clock (or game clock)
A device made up of two adjacent clocks and buttons, keeping track of the total time each player takes for their moves. Immediately after moving, the player hits his button, which simultaneously stops his clock and starts his opponent's. The picture shown displays an analogue clock where the term flag fall originates. Modern clocks are digital.
chess notation
See algebraic notation and descriptive notation.
chess problem
Also called composition.
chess variant
A chess-like game played using a different board, pieces, or rules than standard chess.
chop wood
Slang for making capture(s) or exchange(s). See also wood.
1. An opening system geared towards forming a full pawn center. See also hypermodern.
2. A game using a longer time control such as 40/2; the opposite of fast chess categories such as rapid, blitz or bullet.
classical bishop sacrifice
See Greek gift sacrifice.
1. Removal of pieces from a rank, file or diagonal so that a bishop, rook or queen is free to move along it.
2. Clearing the diagonal : removing pieces from a diagonal so that an enemy bishop, usually a fianchettoed bishop, has no targets to attack.
clock move
In a game played clock move, a move is considered completed only after the clock is pressed. For example, one could touch a piece, then move a different piece—as long as the player has not pressed their clock button. This way of playing is uncommon but can be seen in casual games, rather than in tournaments, which are very likely to use the touch move rule.
clock time
Time (consumed or remaining) on the chess clock, in a tournament game.
closed file
A file on which White and Black each have a pawn.
closed game (or Closed Game)
1. A position with few open lines (files or diagonals), generally characterized by interlocking pawn chains, cramped positions with few opportunities to exchange, and extensive maneuvering behind lines. Such a position may later become an open game. See also positional play.
2. A chess opening that begins with the moves 1.d4 d5, also called a Double Queen's Pawn Opening or Double Queen's Pawn Game. See also Open Game and Semi-Open Game.
closed tournament
A tournament in which only invited or qualifying players may participate, as opposed to an open tournament. Also called an invitational tournament.

The Blackburne Shilling Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Nd4?!), an example of coffeehouse play
Adjective used to describe a move, player, or style of play characterized by risky, positionally dubious play that sets traps for the opponent. The name comes from the notion that one would expect to see such play in skittles games played in a coffeehouse or similar setting, particularly in games played for stakes and/or blitz chess. The Blackburne Shilling Gambit is a typical example of coffeehouse play.
color (or colour)
1. The white or black pieces. See White and Black in chess.
2. May refer to a certain square, for example "1.e4 – White played his king pawn to the light-colored square."
A clever sequence of moves, often involving a sacrifice, to gain the advantage. The moves of the opponent are usually forced (i.e. a combination does not give the opponent too many possible lines of continuation).
An imbalanced reciprocal return. For example, sacrificing material for development, or trading a bishop for one or two pawns.
computer move
Colloquial term for a (typically unthematic or obscure) move more likely to be played by a computer than a human.
connected passed pawns
Passed pawns on adjacent files. These are considered to be unusually powerful (often worth a minor piece or rook if on the sixth rank or above and not properly blockaded) because they can advance together. Also see connected pawns.
connected pawns
Refers to two or more pawns of the same color on adjacent files. See also isolated pawns.
connected rooks
Two rooks of the same color on the same rank or file with no pawns or pieces between them. Connected rooks are usually desirable. Players often connect rooks on their own first rank or along an open file. Cf. doubled rooks.
The improvement of a player's position by the reposition of one or more pieces to better square(s), typically after a player's attack or combination has left his pieces in poor positions or uncoordinated.
control of the centre (or control of the center)
Having one or more pieces that attack any of the four centre squares; an important strategy, and one of the main aims of openings.
1. An unintended solution of a chess problem. See also cook.
2. May more generally refer to a refutation to published analysis.
correspondence chess
This is chess played at a long time control by various forms of long-distance correspondence, usually through a correspondence chess server, through email or by the postal system. Typically, one move is transmitted in every correspondence.
corresponding squares
Squares of reciprocal (or mutual) zugzwang often found in king and pawn endgames. Also known as related squares.
An attack that responds to an attack by the opponent.
A gambit offered by Black, for example the Greco Counter Gambit, usually called the Latvian Gambit today (1.e4 e5 2.Nf3 f5?!); the Albin Countergambit (1.d4 d5 2.c4 e5); and the Falkbeer Countergambit (1.e4 e5 2.f4 d5). An opening need not have "countergambit" in its name to be one; for instance, the Benko Gambit (1.d4 Nf6 2.c4 c5 3.d5 b5), Englund Gambit (1.d4 e5?!), the Budapest Gambit (1.d4 Nf6 2.c4 e5), the Blackburne Shilling Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Nd4?!) and many lines of the Two Knights Defense (e.g. 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 and now 4...Bc5!? [the Wilkes-Barre Variation or Traxler Counterattack], 4...Nxe4?!, 4...d5 5.exd5 Na5 6.Bb5+ c6 [the main line], 4...d5 5.exd5 Nd4 [the Fritz Variation], and 4...d5 5.exd5 b5 [the Ulvestad Variation]) are all examples of countergambits.
Active maneuvering by the player in an inferior or defensive position.
To protect a piece or control a square. For example, in order to checkmate a king on the side of the board, the five squares adjacent to the king must all be covered.
A position with limited mobility.
critical position
1. A position of key importance in determining the soundness of an opening variation. In opening preparation, if one side can demonstrate an advantage in a critical position, the other side must either find an improvement or else abandon that variation as inferior.
2. More generally, any position in a game where the next move(s) are apt to determine the outcome (win, draw, or loss).
critical square
See key square.
A cross-check is a check played in reply to a check, especially when the original check is blocked by a piece which itself either delivers check or reveals a discovered check from another piece.
An arrangement of the results of every game in a tournament in tabular form. The names of the players run down the left side of the table in numbered rows. The names may be listed in order of results, alphabetically, or in pairing order, but results order is most common. The columns are also numbered, each one corresponding to the player in the same numbered row. Each table cell records the outcome of the game between the players on the intersecting row and column, using 1 for a win, 0 for a loss, and ½ for a draw. (In a double round-robin tournament each cell contains two entries, as each pair of players plays two games alternating White and Black.) Every game is recorded twice, once from the perspective of each player. The diagonal cells that correspond to the player playing himself are marked with a * or × or other symbol since they are not used. For examples see Hastings 1895 chess tournament, Nottingham 1936 chess tournament, and AVRO tournament.
Slang for a quick win, especially an overwhelming attack versus poor defensive play. A crushing move is a decisive one.


dark squares
The 32 dark-colored squares on the chessboard, such as a1 and h8. A dark square is always located at a player's left hand corner.
dark-square bishop
One of the two bishops that moves on the dark squares, situated on c1 and f8 in the initial position.
dead draw
A drawn position in which neither player has any realistic chance to win. A dead draw may refer to a position in which it is impossible for either player to win (such as insufficient material), or it may refer to a simple, lifeless position which would require a major blunder before either side would have a chance to win.
This is a chess tactic used to lure a piece to an unfavourable square.
defence (or defense)
1. A move or plan which tries to meet the opponent's attack.
2. An opening played by Black, for example the Scandinavian Defence, King's Indian Defence, English Defence, etc.
The inverse of a decoy (see above). Whereas a decoy involves luring an enemy piece to a bad square, a deflection involves luring an enemy piece away from a good square; typically, away from a square on which it defends another piece or threat. Deflection is thus closely related to overloading.
Wouter Mees at a demonstration board
demonstration board
A large standing chess board used to analyse a game or show a game in progress. Johann Löwenthal invented the demonstration board in 1857.
descriptive notation
An old system of recording chess moves, used primarily in the English and Spanish speaking countries through the 1970s or 1980s. Now replaced by the standard algebraic notation.
1. A piece that seems determined to give itself up, typically either to bring about stalemate or perpetual check.
2. A piece to sell itself as dearly as possible in a situation where both sides have hanging pieces.
In the opening, moving a piece from its original square to make it more active. To redevelop a piece means to move it to a better square after it has already been developed.
A line of squares of the same color touching corner to corner, along which a queen or bishop can move.
discovered attack
An attack made by a queen, rook or bishop when another piece or pawn moves out of its way.
discovered check
A discovered attack to the king. This occurs when a player moves a piece, resulting in another piece putting their opponent's king in check.
A situation whereby capture of a piece is unavoidable despite it having wide freedom of movement. Usually occurs in chess problems.
double attack
Two attacks made with one move: these attacks may be made by the same piece (in which case it is a fork); or by different pieces (a situation which may arise via a discovered attack in which the moved piece also makes a threat). The attacks may directly threaten opposing pieces, or may be threats of another kind: for instance, to capture the queen and deliver checkmate.
double check
A check delivered by two pieces at the same time. A double check necessarily involves a discovered check.
doubled pawns
A pair of pawns of the same color on the same file; generally considered a weakness due to their inability to defend each other.
doubled rooks
A powerful position in which two of a player's rooks are placed on the same file or rank with no other chessmen between them. In this position, they defend each other while attacking both laterally and along the shared row. The position especially can be decisive when achieved during the endgame phase of play.
A game that ends without victory for either player. Most drawn games are draws by agreement. The other ways that a game can end in a draw are stalemate, threefold repetition, the fifty-move rule, and insufficient material. A position is said to be a draw (or a "drawn position" or "theoretical draw") if either player can, through correct play, eventually force the game into a position where the game must end in a draw, regardless of the moves made by the other player. A draw is usually scored as ½ point, although in some matches only wins are counted and draws are ignored.
draw death
Hypothetical scenario whereby elite-level chess players, aided by modern computer analysis, become so good that they never make mistakes, leading to endless drawn games (since chess is widely believed to be drawn with best play from both sides).
drawing line
An opening variation that commonly ends in a draw, for example 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bb5 Nd4 5.Nxd4 exd4 6.e5 dxc3 7.exf6 Qxf6 8.dxc3 Qe5+ 9.Qe2 Qxe2+, a line in the Rubinstein Variation of the Four Knights Game. See Collection of drawing lines.[2] Often such a variation is played because one or both players are eager to draw the game.
drawing weapon
An opening line played with the intent of drawing the game. This may or may not be a line commonly thought of as a drawing line. In high-level chess and correspondence chess, a player well-versed in opening theory may even use as a drawing weapon a sharp opening that has been analyzed to a drawn position in a number of lines, such as the Marshall Attack in the Ruy Lopez, and the Sveshnikov and Poisoned Pawn variations of the Sicilian Defense. One example of the successful employment of a drawing weapon was the 2000 World Chess Championship match between Garry Kasparov and Vladimir Kramnik, where the latter used the Berlin Defense to the Ruy Lopez as a drawing weapon with great effect, drawing all four games with that opening.
An adjective describing a position or game that is likely to end in a draw.
draw odds
A type of chess handicap where one player (Black in an Armageddon game) only has to draw in order to win the match.
See woodpusher.
A style of play in which the activity of the pieces is favoured over more positional considerations, even to the point of accepting permanent structural or spatial weaknesses. Dynamism stemmed from the teachings of the Hypermodern School and challenged the dogma found in more classical teachings, such as those put forward by Wilhelm Steinitz and Siegbert Tarrasch.


The English Chess Federation (ECF) is the governing chess organisation in England and is one of the federations of the FIDE. It was known as the British Chess Federation (BCF) until 2005 when it was renamed.
The Encyclopaedia of Chess Openings (ECO), a standard and comprehensive chess opening reference. Also a classification system (ECO code) for chess openings that assigns an alphanumeric code from A00 to E99 to each opening.
An edge is a small but meaningful advantage in the position against one's opponent. It is often said White has an edge in the starting position, since he moves first (see First-move advantage in chess).
Elo rating system
The Elo rating system is a method for calculating the relative skill levels of chess players, named after the Hungarian Arpad Elo. Since 2012, FIDE publishes a monthly international chess rating list using the Elo system.
en passant
[from French: "in the act of passing"] The rule that allows a pawn that has just advanced two squares to be captured by an enemy pawn that is on the same rank and adjacent file. The pawn can be taken as if it had advanced only one square. Capturing en passant is possible only on the next move.

The pawn on e4 is en prise.
en prise
[from French: "in a position to be taken",[3][4] often italicized] En prise describes a piece or pawn exposed to a material-winning capture by the opponent. This is either a hanging piece, an undefended pawn, a piece attacked by a less valuable attacker, or a piece or pawn defended insufficiently. For instance, 1.e4 Nf6 2.Nf3? leaves White's e-pawn en prise.
The stage of the game when there are few pieces left on the board. The endgame follows the middlegame.
endgame tablebase
A computerized database of endgames with up to seven pieces, providing perfect play for both players, and thus completely solving those endgames. (Six-piece endgames have been finished; some seven-piece endgames have been finished as of 2008.)
Epaulette mate
A checkmate position where the king is blocked on both sides by his own rooks.
An abbreviation for Extended Position Description.
equalise (or equalize)
To create a position where the players have equal chances of winning (referred to as: equality). This may be either static equality, where a draw is likely (for example, a balanced endgame), or certain equality (for example, by perpetual check), or dynamic equality, where White and Black have equal chances of winning the game. In opening theory, since White has the advantage of the first move, lines that equalise are relatively good for Black.
escape square
See flight square.
1. The capture of a pair of pieces, one white and the other black, usually of the same type (i.e., rook for rook, knight for knight, etc.), or of bishop for knight (two pieces that are considered almost equal in value).
2. The advantage of a rook over a minor piece (knight or bishop). The player who captures a rook for a minor piece is said to have "won the exchange", and the opponent is said to have "lost the exchange". An exchange sacrifice is giving up a rook for a minor piece.
exchange variation
This is a type of opening in which there is an early, voluntary exchange of pawns or pieces.
A contest of one or more games played for the purpose of public entertainment, as opposed to a match or tournament. An exhibition may pit two masters against each other, in which case chess clocks are normally used and the contest is quite serious. A simultaneous exhibition/display has one or more masters play many celebrity or amateur opponents at once, and is often not timed.
expanded centre (or expanded center)
The central sixteen squares of the chessboard.
exposed king
A king lacking pawns to shield it from enemy attack.
Extended Position Description (EPD)
A Forsyth-Edwards Notation derivative format that contains the position on the chessboard, but not the game. It is primarily used to test chess engines.


family fork (or family check)
A knight fork that simultaneously attacks the enemy king (giving check), queen, and possibly other pieces.
An abbreviation for figurine algebraic notation, which substitutes symbols for letters to represent piece names (e.g. ♞f3 instead of Nf3).
Fast chess
A form of chess in which both sides are given less time to make their moves than under the normal tournament time controls. See also: Rapid chess, Blitz chess, Bullet chess.
An abbreviation for Forsyth–Edwards Notation.
Refers to a bishop developed to the longest diagonal on the file of the adjacent knight (b2 or g2 for White; b7 or g7 for Black), or the moves to develop a bishop to one of those squares. A fianchetto usually occurs after moving the pawn on that file forward one square (or perhaps two). The Italian word is actually a noun ("in fianchetto") and not a verb.
The World Chess Federation (Fédération Internationale des Échecs), the primary international chess organizing and governing body. The abbreviated name FIDE is nearly always used in place of the full name in French.
FIDE Master (FM)
A chess title ranking below International Master.
fifty-move rule
A draw may be claimed if no capture or pawn move has occurred in the last fifty moves by either side.

The f-file
A column of the chessboard. A specific file can be named either using its position in algebraic notation, a–h, or by using its position in descriptive notation. For example, the f-file or the king bishop file comprises the squares f1–f8 (or KB1–KB8 in descriptive notation).
first board
See top board.
first-move advantage
The slight (by most accounts) advantage that White has by virtue of moving first.
first player
The expression "the first player" is sometimes used to refer to White.
Fischer delay
A time control method with time delay, invented by Bobby Fischer. When it becomes a player's turn to move, the delay is added to the player's remaining time.
Fischer Random (or Fischerandom)
See Chess960.
See woodpusher.
Five-minute chess
See Blitz chess.
Part of an analogue chess clock, usually red, that indicates when the minute hand passes the hour. To "flag" someone means winning the game on the basis of the opponent exceeding the time control.
The queenside a-, b-, and c-file, or the kingside f-, g-, and h-file, also called wing; distinguished from the center d-file and e-file.
flank opening
A chess opening played by White and typified by play on one or both flanks.
flight square
A square to which a piece can move, which allows it to escape attack. Also called escape square. See also luft.
An abbreviation for the FIDE Master title.
focal point
The square upon which a player focuses an attack, for example by repeatedly attacking that square or sacrificing a piece there. For example, in an attack upon an uncastled king, Black's f7-square (or White's f2-square) is a common focal point. Examples of attacks on the focal point f7 include the Fried Liver Attack (initiated by a knight sacrifice on f7) and the primitive Scholar's mate (ending with checkmate on f7).
Fool's mate
Fool's mate
The shortest possible chess game ending in mate: 1.f3 e5 2.g4 Qh4# (or minor variations on this).
forced mate
A sequence of two or more moves culminating in checkmate that the opponent cannot prevent.
forced move
A move that is the only one which does not result in a serious disadvantage for the moving player. Forced can also be used to describe a sequence of moves for which the player has no viable alternative, for example "the forced win of a piece" or "a forced checkmate". In these cases the player cannot avoid the loss of a piece or checkmate, respectively.
Refers to losing the game by absence or by exceeding the time control (forfeit on time).
A simultaneous attack by a single piece on two (or more) of the opponent's pieces (or other direct target, such as a mate threat). When the attacker is a knight the tactic is often specifically called a knight fork. Some sources state that only a knight can give a fork and that the term double attack is correct when another piece is involved, but this is by no means universal usage.
Forsyth–Edwards Notation (FEN)
A standard notation for describing a particular board position of a chess game. The purpose of FEN notation is to provide all the necessary information to restart a game from a particular position.
A fortress is a position that, if obtained by the weaker side, will prevent penetration by the opposing side, this generally resulting in a draw (which the weaker side is seeking).
friendly game
A game that is not played as part of a match, tournament, or exhibition. Often the game is not timed, but if a chess clock is used rapid time controls are common. The term refers only to the circumstances in which the game is played, not the relationship between the players or the intensity of the competition. Also called a casual game.


A sacrifice (usually of a pawn) used to gain an early advantage in space and/or time in the opening.
game score
The record of a game in some form of notation. In over-the-board tournaments, the game score is recorded on a score sheet.
An abbreviation for Grandmaster.
good bishop
A bishop that has high mobility, typically because the player's pawns are on squares of color opposite to that of the bishop. See also bad bishop.
Grandmaster (GM)
The highest title a chess player can attain (besides World Champion). When used precisely, it is the title awarded by FIDE starting in 1950, but it can be used to describe someone of comparable ability. The term International Grandmaster or IGM would refer only to the FIDE title.
grandmaster draw
A game in which the players quickly agree to a draw after making little or no effort to win. This may be a very boring game, for example 1.d4 d5 2.c4 c6 3.cxd5 cxd5 4.Nc3 Nf6 5.Nf3 Nc6 6.Bf4 Bf5 7.e3 e6 ½–½ (draw agreed), or a superficially exciting game played with a variation the players know leads to a draw, for example 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6 5.0-0 Bg4 6.h3 h5 7.c3 Qd3 8.hxg4 hxg4 9.Nxe5 Bd6 (a pseudo-sacrifice of Black's queen) 10.Nxd3 Bh2+ 11.Kh1 Bd6+ and Black draws by perpetual check. Although originally used to refer to such games between grandmasters, the term is now used colloquially to refer to any such game.
Greek gift sacrifice
Also known as the classical bishop sacrifice, it is a typical sacrifice of a bishop by White playing Bxh7+ or Black playing Bxh2+ against a castled king to initiate a mating attack.


half-open file
A file on which only one player has no pawns.
See odds.
Unprotected and exposed to capture. It is not the same as en prise since a piece en prise may be protected. To "hang a piece" is to lose it by failing to move or protect it.
hanging pawns
Two friendly pawns abreast without friendly pawns on adjacent files. Hanging pawns can be either a strength (usually because they can advance) or a weakness (because they cannot be defended by pawns) depending on circumstances.
Harrwitz bishops
A player's light-square and dark-square bishops placed so that they occupy adjacent diagonals; named for the mid-19th century master Daniel Harrwitz. For example, White has Harrwitz bishops in the Danish Gambit after 1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2. Harrwitz bishops can be a potent attacking force in the middlegame. Also called raking bishops.
heavy piece
See major piece.

The dots indicate holes. (Evans, 1967)
A square that a player does not, and cannot in future, control with a friendly pawn. The definition is somewhat subjective: the square must have some positional significance for the opponent to be considered a hole – squares on the first and second ranks are not holes. On the other hand a square is a hole even if it can be controlled in the future with a pawn that has made a capture. An example of a hole is the e4-square in the Stonewall Attack.
home rank
Rank one for White; rank eight for Black. See back rank.
horizontal line
See rank.
Horwitz bishops (or Horrwitz bishops)
Synonym for Harrwitz bishops used by Nimzowitsch in My System possibly in reference to Bernhard Horwitz.
human move
a move a human would make, as opposed to the kind of move that only a computer would make.
Hutton pairing
A pairing technique invented in 1921 by George Dickson Hutton for matching teams of players in which only one game is required per player. Has been used regularly for correspondence team events and for matches between many teams conducted on one day. Also called jamboree pairing.
Describes an opening system geared towards controlling the center with pieces from the flanks as opposed to occupying it with pawns. See also classical.


See International Correspondence Chess Federation.
An abbreviation for the International Correspondence Chess Federation.
An abbreviation for Internet chess server.
An abbreviation for the older term International Grandmaster. The modern usage is Grandmaster (GM).
illegal move
A move that is not permitted by the rules of chess. An illegal move discovered during the course of a game must be corrected.
illegal position
1. A position in a game that is a consequence of an illegal move or an incorrect starting position.
2. In chess problems, an illegal position is one that is impossible to reach in a game by any sequence of legal moves.
An abbreviation for the International Master title.
A difference between positions of the white and black pieces. An imbalanced position is one where White and Black both have unique adavntages and chance to win by using those advantages. Conversely, a balanced position is often more drawish.
A move that is not the best, but not as bad as a blunder.
See passive.
Refers to the amount of time added to each player's time before each move. For instance, Rapid chess might be played with "25 minutes plus 10 second per move increment", meaning that each player starts with 25 minutes on their clock, and this increments by 10 seconds after (or before) each move, usually using the Fischer Delay method. See Time control#Compensation (delay methods).

In the KID Fianchetto Variation (1.d4 Nf6 2.c4 g6 3.Nf3 Bg7 4.g3 0-0 5.Bg2 d6 6.0-0), both sides have Indian bishops.
Indian bishop
A fianchettoed bishop, characteristic of the Indian defences, the King's Indian and the Queen's Indian.
Indian defence (or Indian defense)
A chess opening that begins 1.d4 Nf6. Originally used to describe queen's pawn defences involving the fianchetto of one or both black bishops, it is now used to describe all Black defences after 1.d4 Nf6 that do not transpose into the Queen's Gambit.
The advantage a player who is making threats has over his opponent who must respond to them. The attacking player is said to "have the initiative" and can often dictate the turn of play. The initiative often results from an advantage in time and/or space. The notion of the initiative was used by Steinitz (e.g. The Sixth American Chess Congress) and by Capablanca in his Chess Fundamentals (Chapter 4).
insufficient material
An endgame scenario in which all pawns have been captured, and one side has only its king remaining while the other has only its king, a king plus a knight, or a king plus a bishop. A king plus bishop versus a king plus bishop with the bishops on the same color is also a draw, since neither side can checkmate, regardless of play. Situations where checkmate is possible only if the inferior side blunders are covered by the fifty-move rule. See Draw (chess)#Draws in all games.
The interruption of the line between an attacked piece and its defender by sacrificially interposing a piece.
intermediate move
See zwischenzug.
International Arbiter
A tournament official who arbitrates disputes and performs other duties such as keeping the score when players are under time pressure.
International Correspondence Chess Federation (ICCF)
The International Correspondence Chess Federation was founded in 1951 to replace the International Correspondence Chess Association (ICCA).
International Grandmaster (IGM)
The original name of the FIDE title now simply called Grandmaster (GM).
International Master (IM)
A chess title that ranks below Grandmaster but above FIDE Master.
Internet chess server (ICS)
An external server that provides the facility to play, discuss, and view chess over the Internet.
To move a piece between an attacking piece and its target, blocking the line of attack. Interposing a piece is one of the three possible responses to a check (the others being to move the king, or capture the attacking piece).
Interzonal tournament
A tournament organised by the FIDE, the second qualifying cycle of the World Chess Championship. The participants are selected from the top players of the Zonal tournaments. The top ranking players qualify for the Candidates Tournament.

Italian bishops in the Giuoco Piano
An abbreviation for isolated queen pawn. See also isolani.
irregular opening
Irregular openings are chess openings with an unusual first move from White. These openings are all categorized under the ECO code A00.
Refers to a d-pawn with no pawns of the same color on the adjacent c-file and e-file, and is a synonym for isolated queen pawn. The term was coined by Nimzowitsch, who considered the isolani as a weapon of attack in the middlegame but an endgame weakness; he considered the problem of hanging pawns to be related. See also Pawn structure#The Queen's Gambit – Isolani.
isolated pawn
A pawn with no pawn of the same color on an adjacent file.
Italian bishop
A white bishop developed to the c4-square or a black bishop developed to c5. A bishop so developed is characteristic of the Italian Game, 1.e4 e5 2.Nf3 Nc6 3.Bc4 (particularly the Giuoco Piano, 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5, where both players have Italian bishops), and stands in contrast to the "Spanish" bishop on b5 characteristic of the Ruy Lopez. Likewise, "Italian" may be used as an adjective denoting an opening where one or both players has an Italian bishop, such as after 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bc4, the Italian Four Knights Game.


J'adoube (see Touch-move rule)
[from French] "I adjust", pronounced: [ʒa.dub]. A player says "J'adoube" as the international signal that he intends to adjust the position of a piece on the board without being subject to the touched piece rule.


Symbol used for the king when recording chess moves in English.
Keizer system
A pairing system where a player plays an opponent who is close in the ranking. Named after the Dutch inventor of the system, and useful when the number of participants exceeds the number of playing rounds. See also Swiss tournament and round-robin tournament.
key square
1. An important square.
2. In pawn endings, a square whose occupation by one side's king guarantees the achievement of a certain goal, such as the promotion of a pawn or the win of a pawn.
The King's Gambit Accepted chess opening.
The King's Gambit Declined chess opening.
The King's Indian Attack chess opening.
As a spectator, making comments on a chess game that can be heard by the players. Kibitzing on a serious game while it is in progress (rather than during a post-mortem) is a serious breach of chess etiquette.
Attacking a piece, typically by a pawn, so that it will move. Kicking a piece may lead to gaining a tempo, or may force the opponent to concede control of key squares.
The King's Indian Defence chess opening.
Chess king icon.png see king
king bishop (or king's bishop)
The bishop that was on the kingside at the start of the game. The terms king knight and king rook are also used. Sometimes abbreviated "KB", "KN", and "KR" respectively.
king hunt
A sustained attack on the enemy king that results in the king being driven a far distance from its initial position, typically resulting in its checkmate. Some of the most famous games featuring king hunts are Edward Lasker–Thomas, Polugaevsky–Nezhmetdinov, and Kasparov–Topalov.[5]
king knight (or king's knight)
The knight that was on the kingside at the start of the game. The terms king bishop and king rook are also used. Sometimes abbreviated "KN", "KB", and "KR" respectively.
king pawn (or king's pawn)
A pawn on the king's file, i.e. the e-file. Sometimes abbreviated "KP". Also king bishop pawn (KBP), king knight pawn (KNP), and king rook pawn (KRP) for a pawn on the f-, g-, or h-file respectively.
kingside (or king's side)
The side of the board (board-half) the kings are on at the start of the game (the e- through h-file), as opposed to the queenside.
Chess knight icon.png see knight
knight pawn (or knight's pawn)
A pawn on the knight's file, i.e. the b-file or g-file. Sometimes abbreviated "NP".
Example of a knight's tour
knight's tour
A mathematical treatment of a knight "touring" the chessboard, i.e. repeatedly moving as it does in the game so as to visit each square exactly once.
knockout tournament (see Single-elimination tournament)
A tournament conducted as a series of matches in which the winner of each match advances to the next round and the loser is eliminated. Well-known chess tournaments held in the knockout format include London 1851 and the 2007 Chess World Cup. Cf. round-robin tournament and Swiss tournament.
Kotov syndrome
This phenomenon, first described by Alexander Kotov, can occur when a player does not find a good plan after thinking long and hard on a position. The player, under time pressure, then suddenly decides to make a move, often a terrible one which was not analysed properly.
A popular chess variant in which players do not know the moves of the other and determine their moves based on limited information from a monitoring umpire. This variant of the game is sometimes referred to as blind chess, but should not be confused with blindfold chess.
The symbol sometimes used for the knight when recording chess moves in descriptive notation, mainly in older literature. An N is used instead in algebraic notation and in later descriptive notation to avoid confusion with K, the symbol for the king.


Slang for queen. To "bring out the lady" means to develop the queen.
laws of chess
The rules of chess.
light squares
The 32 light-colored squares on the chessboard, such as h1 and a8.
light-square bishop
One of the two bishops moving on the light squares, situated on f1 or c8 in the initial position.
Lightning chess
A form of chess with an extremely short time limit, either Blitz chess or Bullet chess.
1. A sequence of moves, usually in the opening or in analyzing a position.
2. An open path for a piece (queen, rook, or bishop) to move or control squares.
A piece whose movement is defined to be along straight lines of squares (i.e. the rook, bishop, and queen).
See simplification.
long diagonal
One of the two diagonals with eight squares (a1–h8 or h1–a8).

Lucena position
long-range piece
A bishop, rook, or queen.
loose piece
A piece vulnerable to opponent attacks because it is undefended and cannot easily be withdrawn or supported.
loose position
A position vulnerable to opponent attacks because it is overextended or its pieces are uncoordinated.
Slang for a move that loses the game.
A defeat for one of the two players, which may occur due to that player being checkmated by the other player, resigning, exceeding the time control, or being forfeited by the tournament director. Chess being a zero-sum game, this results in a win for the other player, except in the very rare circumstance where the tournament director forfeits both players, for example for cheating or both players exceeding the time control (the latter does not normally result in a double forfeit today).
Lucena position
A well-known rook and pawn versus rook endgame position in which the player with the extra pawn can force a win.
[from German: air] Space made for a castled king to give it a flight square to prevent a back-rank mate. Usually luft is made by moving a pawn on the second rank in front of the king. See also flight square.


main line
The principal, most important, or most often played variation of an opening or piece of analysis. For example, 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.0-0 Nc6 8.d5 Ne7 is often referred to as the main line of the King's Indian Defence.
major piece
A queen or rook, also known as a heavy piece.
A larger numbers of pawns on one flank opposed by a smaller number of the opponent's; often a player with a majority on one flank has a minority on the other.
A piece or a pawn, when the term piece is used as exclusive of pawns. Note that even the queen is considered a man.

A typical Maróczy Bind position
Maróczy Bind
A bind on the light squares in the centre, particularly d5, obtained by White by placing pawns on c4 and e4. Named for Géza Maróczy, it originally referred to formations arising in some variations of the Sicilian Defence, but the name is now also applied to similar setups in the English Opening and the Queen's Indian Defence. It was once greatly feared by Black but means of countering it have been developed since the 1980s and earlier.
A competition between two individuals or two teams. A match may be the entire competition, or it may be a round in a knockout tournament or team tournament. Unlike in some sports where the word match is sometimes used to describe a single game, a chess match always consists of at least two games (and often many more).
Short for checkmate.
All of a player's pieces and pawns on the board. The player with pieces and pawns of greater value is said to have a "material advantage". When a player gains a material advantage they are also said to be "winning material". See Chess piece relative value.
Playstyle characterised by a willingness to win material at the expense of positional considerations. Chess computers are often materialistc.
mating attack
An attack aimed at checkmating the enemy king.
mating net
A position or series of moves that leads to forced mate.
Modern Chess Openings, a popular chess opening reference. Often the edition is also given, as in "MCO-14", the 14th edition. Cf. ECO.
The part of a chess game that follows the opening and comes before the endgame, beginning after the pieces are developed in the opening. This is usually roughly moves 20 through 40.
A short game (usually no more than 20 to 25 moves), for example: 1.e3 e5 2.Qf3 d5 3.Nc3 e4 4.Qf4?? Bd6! and White resigned in NN–Künzel (1900, Europe)[6] because his queen is trapped. However, a significant minority of authors include games up to 30 moves.[7] Usually only decisive games (not draws) are considered miniatures. Ideally, a miniature should not be spoiled by an obvious blunder by the losing side. A miniature may also qualify as a brilliancy. The Opera game is a famous example. Sometimes called a brevity [chiefly British].
minor exchange
The exchange of a bishop for a knight.
minor piece
A bishop or knight.
minority attack
An advance of pawns on the side of the board where one has fewer pawns than the opponent, usually carried out to provoke a weakness.
mobile pawn centre (or mobile pawn center)
Pawns on central squares able to advance without becoming weak.
The ability of a piece, or of a player's pieces collectively, to move around the board. (In computer chess this is often measured by the number of legal moves available.) Effectively means much the same as space.
A full move is a turn by both players, White and Black. A turn by either White or Black is a half-move, or (in computer context) one ply.
move order
The sequence of moves one chooses to play an opening or execute a plan. Different move orders often have different advantages and disadvantages. For example, 1.d4 Nf6 2.Nf3 avoids the Budapest Gambit (2.c4 e5!?), but makes it impossible for White to play the Sämisch Variation (2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.f3) or Four Pawns Attack (5.f4) against the King's Indian Defence, and to transpose to certain lines of the Nimzo-Indian Defence and Queen's Gambit Declined, Exchange Variation where the knight goes to e2 instead of f3. See transposition.
mysterious rook move
Following Nimzowitsch's idea, a move with a rook that seems to have no threat or purpose, but which actually discourages the opponent from a certain type of action (prophylaxis), or sets up a very deep, well-concealed plan.


Symbol used for the knight when recording chess moves in English.
An abbreviation sometimes used for the chess opening reference Nunn's Chess Openings. Cf. ECO and MCO.
NN (or N.N.)
Used in a game score in place of a player whose name is not known. The origin of this usage is uncertain. It may be an abbreviation of the Latin nomina (names), it may be short for the Latin phrase nomen nescio, "name unknown" (literally "I do not know the name") or it may come from the use of "N or NN" (later read as "N or M") in the Anglican Catechism. See also Amateur.
A performance at a chess tournament that indicates a player is ready to receive a title, or the level of performance needed. In addition to other requirements, a certain number of norms is generally required to earn a title. See Grandmaster and International Master.
See Theoretical novelty (TN).


Odds (or Handicap)
This refers to the stronger player giving the weaker player some sort of advantage in order to make the game more competitive. It may be an advantage in material, in extra moves, in time on the clock, or some combination of those elements. Since the advent of the chess clock, time odds have become more common than material odds. In "time odds" the stronger player may begin the game with only one or two minutes on the clock, while the weaker player may be given five or more minutes on the clock.
Offhand game
See skittles.
An international team chess tournament organized biennially by FIDE. Each team represents a FIDE member country.
O-O (or 0-0)
The move notation for kingside castling. (PGN format uses Os; FIDE uses 0s.)
O-O-O (or 0-0-0)
The move notation for queenside castling. (PGN format uses Os; FIDE uses 0s.)
Open file
A file on which there are no pawns. A file on which only one player has no pawns is said to be half-open.
Open game (or Open Game)
1. A game in which exchanges have opened files and diagonals, as opposed to a closed game.
2. A chess opening that begins with the moves 1.e4 e5 (also called a Double King's Pawn Opening or Double King's Pawn Game). See also Closed Game and Semi-Open Game.
Open tournament
A tournament where anyone can enter, regardless of rating or invitation. Cf. closed tournament.
The beginning moves of the game, roughly the first 10–20 moves. In the opening players set up their pawn structures, develop their pieces, and typically castle. The opening precedes the middlegame.
Opening preparation
Home study and analysis of openings and defenses that one expects to play, or meet, in later tournament or match games. In high-level play, an important part of this is the search for theoretical novelties that improve upon previous play or previously published analysis.
Opening repertoire
The set of openings played by a particular player. The breadth of different players' repertoires varies from very narrow to very broad. For example, a player who always opens with 1.e4; always meets 1.e4 with the Sicilian Defence, and the Najdorf Variation of it if allowed; and always meets 1.d4, 1.c4, or 1.Nf3 with 1...f5, intending to play the Dutch Defence, has a very narrow opening repertoire. Bent Larsen, who opened at various times with 1.e4, 1.d4, 1.c4, 1.f4, 1.Nf3, 1.b3, and 1.g3, and played a large number of different defences as Black, had a very broad opening repertoire.
Opening system
An opening, such as the Colle System or Hippopotamus Defence, that is defined by one player's moves, which can be played regardless of the moves of the opponent.
Opposite-colored bishops (or Opposite-coloured bishops)
See bishops on opposite colors.
A situation in which two kings stand on the same rank, file or diagonal with one empty square between them. The player to move may be forced to move the king to a less advantageous square. Opposition is a particularly important concept in endgames.
Optimal play (see Best response)
Both sides playing their best move at each turn, or one of equally good alternatives. One side tries to win as quickly as possible while the other side tries to delay it as long as possible, or optimal play may result in a draw.
An abbreviation for over the board.
An outpost is a square protected by a pawn that is in or near the enemy's stronghold. Outposts are a favourable position from which to launch an attack, particularly using a knight.
Outside passed pawn
A passed pawn that is near the edge of the board and far away from other pawns. In the endgame, such a pawn often constitutes a strong advantage for its owner.
A position where a player has moved a piece or group of pieces (usually pawns) away from the rest in such a way that they are too difficult to defend.
A piece that has too many defensive duties. An overloaded piece can sometimes be deflected, or required to abandon one of its defensive duties.
The strategy of protecting a pawn or specific square of the chessboard more than is immediately necessary. This serves to dissuade the opponent from attacking that specific point and provides greater freedom of movement for the pieces protecting that square. This can cause an opponent to pursue a faulty plan or no plan at all. Aron Nimzowitsch was one of the foremost proponents of overprotection.
A move made in error, usually a blunder, due to a miscalculation or missed observation.
Over the board (OTB)
A game played face-to-face with the opponent, as opposed to a remote opponent as in online chess or correspondence chess.
A synonym for overloaded.


The assignment of opponents in a tournament. Pairing is made more difficult in chess because of the need to try to give each player an equal number of games playing White and Black and to try to not assign a player the same color in too many consecutive games. The most common pairing methods used in chess tournaments are round-robin and the Swiss system.
Passed pawn
A pawn that has no pawn of the opposite color on its file or on any adjacent files on its way to queening.
A passed pawn.
1. A piece that is able to move to or control relatively few squares, also referred to as an inactive piece.
2. A "passive position" is a position offering little prospect of attack. A "passive defense" is a defense offering little prospect of counterattack.
Antonym: active.
Passive sacrifice
The sacrifice of a piece, by moving a different piece, leaving the sacrificed piece under attack.
A weak chess player [German: patzen, to bungle]. See also woodpusher.
Chess pawn icon.png see pawn
Pawn and move
A type of odds game, common in the 18th and 19th centuries, in which the superior player plays Black and begins the game with one of his pawns, usually the king bishop pawn, removed from the board.

Pawn chains in the French Defence
Pawn centre (or Pawn center)
A player's pawns in the board centre. By extension, pawns on the squares adjacent to the centre may also be considered as part of the pawn centre. Having an ample pawn centre was considered a huge advantage until the hypermodernist school nuanced this judgment. See King's Indian Defence, Four Pawns Attack for an example of an opening leading to an extended pawn centre.
Pawn chain
A locked diagonal formation of pawns, each one supported by a friendly pawn diagonally behind and blocked by an enemy pawn directly ahead. Aron Nimzowitsch considered pawn chains extensively, and recommended attacking the enemy pawn chain at its base. See pawn structure.
Pawn island
A group of pawns of one color on consecutive files with no other pawns of the same color on any adjacent files. A pawn island consisting of one pawn is called an isolated pawn.
Pawn race
A situation where both opponents are pushing a passed pawn in effort to be first to promote.
Pawn storm
An attacking technique where a group of pawns on one wing is advanced to break up the defence.
Pawn structure
The placement of the pawns is known as the pawn structure. As pawns are the least mobile of the pieces and the only pieces unable to move backwards, the position of the pawns greatly influences the character of the game.
An abbreviation for the Professional Chess Association.
Performance rating
A number reflecting the approximate rating level at which a player performed in a particular tournament or match. It is often calculated by adding together the player's performances in each individual game, using the opponent's rating for a draw, adding 400 points to the opponent's rating for a win, and subtracting 400 points from the opponent's rating for a loss, then dividing by the total number of games. For example, a player who beat a 2400-rated player, lost to a 2600, drew a 2500, and beat a 2300, would have a performance rating of 2550 (2800 + 2200 + 2500 + 2700, divided by four).
Perpetual check
A draw forced by one player putting the opponent's king in a potentially endless series of checks.
An abbreviation for Portable Game Notation.
Philidor position
Usually refers to an important chess endgame which illustrates a drawing technique when the defender has a king and rook versus a king, rook, and pawn. It is also known as the third rank defence, because of the importance of the rook on the third rank cutting off the opposing king. It was analyzed by Philidor in 1777. See also Rook and pawn versus rook endgame.
One of the chessmen or figures used to play the game—king, queen, rook, bishop, knight or pawn. Each piece type has its own rules of movement on the board. The word "piece" can refer to any chess piece including pawns (as in the touched piece rule), or it can refer to a minor piece (as in "I hung a piece"), depending on context. It can also mean a major or minor piece, as in "White needs to get some pieces to the kingside."
When a piece cannot move (either legally or advisedly) because doing so would expose a valuable piece, usually the king or queen, to attack. Pins against the king are called absolute because it is then illegal to move the pinned piece. Other pins are called relative pins.
A strategy used by a chess player to make optimal use of his advantages in a specific position while minimizing the impact of his positional disadvantages.
Said of an opening or move that gives the person playing it a tenable position, for example "Petroff's Defense is playable." or (after 1.e4 e5 2.Bc4 Nf6 3.Nc3 Nxe4 4.Nxe4) "4... d5 is the only playable move", implying that there are other legal moves, but they all leave the player in a worse position.
Term mainly used in computer chess to denote one play of either White or Black. Thus equal to half a move.

Black has accepted the "poisoned" b2-pawn with 8...Qxb2 in the Sicilian Defence, Najdorf Variation.
An abbreviation for Portable Game Notation.
Poisoned pawn
An unprotected pawn which, if captured, causes positional problems or material loss.
Poisoned Pawn Variation
A variation of the Najdorf Variation of the Sicilian Defence, where some players call White's pawn on b2 a poisoned pawn since capturing it is dangerous for Black.
Portable Game Notation (PGN)
This is a popular computer-processible ASCII format for recording chess games (both the moves and related data).
Positional play
Play dominated by long-term maneuvering for advantage rather than by short-term attacks and threats, and requiring judgment more than extensive calculation of variations, as distinguished from tactics.
Positional player
A player who specializes in positional play, as distinguished from a tactician.
Positional sacrifice
A sacrifice in which the lost material is not regained via a combination, but instead gains positional compensation. These typically require deep positional understanding and are often overlooked by computers. Also known as a "true sacrifice", as opposed to a pseudo-sacrifice or sham sacrifice.
Analysis of a game after it has concluded, typically conducted by one or both players and sometimes spectators (kibitzers) as well.
Prepared variation
A well-analyzed novelty in the opening which is not published but first used against an opponent in competitive play.
a Russian term for simple strategic devices that depend on pawn structure.
Professional Chess Association (PCA)
The Professional Chess Association (PCA) was a rival organisation to FIDE, the international chess organization. The PCA was created in 1993 by Garry Kasparov and Nigel Short for the marketing and organization of their chess world championship. The PCA lost its main sponsor, Intel, in 1996 and folded soon after.
Advancing a pawn to the eighth rank, converting it to a queen, rook, bishop or knight. Promotion to a piece other than a queen is called underpromotion.
[adjective: prophylactic] Prophylactic techniques include the blockade, overprotection, and the mysterious rook move.
1. A move that frustrates an opponent's plan or tactic.
2. A strategy in which a player frustrates tactics initiated by the opponent until a mistake is made.
Protected passed pawn
A passed pawn that is supported by another pawn.
See sham sacrifice.
To move a pawn forward.


Symbol used for the queen when recording chess moves in English.
The Queen's Gambit Accepted chess opening.
The Queen's Gambit Declined chess opening.
The Queen's Indian Defence chess opening.
A round-robin style tournament between four players, where each participant plays every other participant once.
1. Chess queen icon.png see queen
2. Also used as a verb for the act of promoting to a queen, for example "to queen the pawn". Cf. promotion.
Queen bishop
(or queen's bishop)
The bishop that was on the queenside at the start of the game. The terms queen knight and queen rook are also used. Sometimes abbreviated "QB", "QN", and "QR" respectively.
Queen pawn
(or queen's pawn)
A pawn on the queen's file, i.e. the d-file. Sometimes abbreviated "QP". Also queen rook pawn (QRP), queen knight pawn (QNP), and queen bishop pawn (QBP) for a pawn on the a-, b-, or c-file respectively.
Promotion to a queen. Also called promotion. Rarely used to indicate promotion to a knight, rook, or bishop as well (underpromotion).
(or queen's side)
The side of the board (board-half) the queens are on at the start of the game (the a- through d-file), as opposed to the kingside.
Quickplay finish
Same as sudden death.
Quiet move
A move that does not attack or capture an enemy piece.


Symbol used for the rook when recording chess moves in English.
Raking bishops
Another term for Harrwitz bishops.

White ranks are indicated at the left (a-file); Black ranks are indicated at the right (h-file).
A row of the chessboard. In algebraic notation, ranks are numbered 1–8 starting from White's side of the board; however, players customarily refer to ranks (but not files) from their own perspectives. For example: White's king and other pieces start on his first (or "back") rank, whereas Black calls the same rank the eighth rank; White's seventh rank is Black's second; and so on. If neither perspective is given, White's view is assumed. This relative reference to ranks was formalized in the older descriptive notation.
Rapid chess (see Fast chess)
A form of chess with reduced time limit, usually 30 minutes per player.
To demonstrate that a strategy, move, or opening is not as good as previously thought (often, that it leads to a loss), or that previously published analysis is unsound. A refutation is sometimes colloquially referred to as a bust. A refutation in the context of chess problems or endgame studies is often called a cook.
Related squares
See corresponding squares.
Relative pin
A pin, where it is legal to move the pinned piece. See also absolute pin.
Reserve tempo
A move a player has available, though superfluous to the game position, may have great effect by virtue of passing the turn to one's opponent.
To concede loss of the game. A resignation is usually indicated by stopping the clocks, and sometimes by offering a handshake or saying "I resign". The traditional way to resign is by tipping over one's king, but this is rarely done nowadays.[8] In master and serious amateur play, it is much more common for a game to be resigned than for it to end with checkmate, because experienced players can foresee checkmate well in advance.
Romantic chess
Romantic chess was the style of chess prevalent in the 19th century. It is characterized by bold attacks and sacrifices.
Chess rook icon.png see rook
Rook lift
A maneuver that places a rook in front of its own pawns, often on the third or fourth rank. This can allow the rook to treat a half-open file as if it were an open file, or a closed file as if it were half-open.
Rook pawn
A pawn on the rook's file, i.e. the a-file or h-file.
Round-robin tournament
This is a tournament in which each participant plays every other participant an equal number of times, for example in the Hastings 1895 chess tournament. In a double round-robin tournament the participants play each other exactly twice, once with white and once with black, for example in the Piatigorsky Cup. A round robin tournament is commonly used if the number of participants is relatively small. See also Swiss tournament.
Royal fork
A fork between king and queen.
Royal piece
1. A king or queen.
2. In the context of variants and fairy chess, the piece subject to check and checkmate, as the king is in orthodox chess.
Royal powers
Refers to unique attributes of the king: being subject to check and checkmate, and the king's ability to castle.


Scholar's mate
Alternate notation for the knight piece. Used rather than the K, which is for king. From the German Springer [English: "jumper"].
Short for sacrifice, usually used to describe a sacrifice for a mating attack.
A move or capture that voluntarily gives up material in return for an advantage such as space, development, or an attack. A sacrifice in the opening is called a gambit.
An abbreviation for standard (or short) algebraic notation (e.g. 1.Nf3), as opposed to long algebraic notation (e.g. 1.Ng1-f3).
Sans voir
[from French] See blindfold chess.
Scholar's mate
A four-move checkmate (common among novices) in which White plays 1.e4, follows with Qh5 (or Qf3) and Bc4, and finishes with 4.Qxf7#.
A record of the moves of a particular game, usually expressed in algebraic notation.
A score sheet
Score sheet
The sheet of paper used to record a game in progress. During formal games, it is usual for both players to record the game using a score sheet. A completed score sheet contains the game score.
Sealed move
Lengthy OTB games can be adjourned. To prevent unfair advantage, the players can agree on the next move being secretly recorded in a sealed envelope. Upon resumption, the arbiter makes the sealed move and the game continues. See also adjournment.
An assistant, often hired to help a player in preparation for and during a major match or tournament. The second assists the players in areas such as opening preparation.[9] The second also assisted with adjournment analysis, before the practice of adjournments was abandoned in the 1990s.
Second player
The expression "the second player" is sometimes used to refer to Black.
See windmill.
Semi-Closed Game
A chess opening that begins with White playing 1.d4 and Black replying with a move other than 1...d5. See also Open Game and Closed Game.
Semi-Open Game
A chess opening that begins with White playing 1.e4 and Black replying with a move other than 1...e5. Also called Half-Open or Asymmetrical King Pawn openings. See also Open Game and Closed Game.
Sham sacrifice
An offer of material which is made at no risk, as acceptance would lead to the gain of equal or greater material or checkmate. This is in contrast to a true sacrifice in which the compensation is less tangible. Also called a pseudo-sacrifice.
Risky, double-edged, highly tactical. Sharp can be used to describe moves, maneuvers, positions, and styles of play.
Slang for an unexpected or sharp move that typically makes a tactical threat and/or technical challenge for the opponent.
A strategy of exchanging pieces of equal value. Simplification can be used defensively to reduce the size of an attacking force. It can also be used by a player with an advantage to amplify that advantage or reduce the opponent's counterplay. Simplification is also used as an attempt to obtain a draw, or as an attempt to gain an advantage by players who are strong in endgame play with simplified positions. Also liquidation and trading.
A simultaneous exhibition
Simultaneous chess
A form of chess in which one (usually expert) player plays against several (usually novice) players simultaneously. Is often an exhibition.
An attack to a valuable piece, compelling it to move to avoid capture and thus exposing a less valuable piece which can then be taken.
A casual or "pick-up" game, usually played without a chess clock. At chess tournaments, a skittles room is where one goes to play for fun while waiting for the next formal game.
Smothered mate
A checkmate delivered by a knight in which the mated king is unable to move owing to it being surrounded (or smothered) by its own pieces. This could occur, for example, after 1.e4 Nc6 2.Ne2 Ne5, and now either 3.c3?? Nd3# or 3.g3?? Nf3#. Smothered mate is often achieved by sacrificing the queen.
Sofia rules
In the tournament played by Sofia rules, players are not allowed to draw by agreement. They could have draws by stalemate, threefold repetition, fifty-move rule, or insufficient material. Other draws are only allowed if the arbiter declares the game reached a drawn position.
An adjective used to describe a move, opening, or manner of play that is characterized by minimal risk-taking and emphasis on quiet positional play rather than wild tactics.
Correct. A sound sacrifice has sufficient compensation, a sound chess opening or variation has no known refutation, and a sound composition has no cooks.
The squares controlled by a player. A player controlling more squares than the other is said to have a spatial advantage. Effectively means much the same as mobility.
Spanish bishop
A white king bishop developed to the b5-square. This is characteristic of the Ruy Lopez, also known as the Spanish Opening.
Speed chess
See Blitz chess.
Spite check
A harmless check given by a player who is about to be checkmated that serves no purpose other than to momentarily delay the defeat.
1. Gradually increasing the pressure of a bind.
2. Sometimes a synonym for zugzwang that is not a mutual zugzwang.
A position in which the player whose turn it is to move has no legal move and his king is not in check. A stalemate results in an immediate draw.
Staunton chessmen
Staunton chess set
The standard design of chess pieces, required for use in competition.
Stem game
A stem game is the chess game featuring the first use of a particular opening variation. Sometimes, the player or the venue of the stem game is then used to refer to that opening.
Strategic crush
Win characterised by gradual accumulation of advantages and complete prevention of counterplay.
Evaluation of game positions and setting up goals and longer-term plans for future play, as opposed to a tactic which is a shorter-term plan typically consisting of a well-defined sequence of moves and their contingent moves from a given game position.
Strength (or Strong)
A forceful or good move, a position having good winning chances, a highly rated player or one successful in tournaments, or a tournament having a sizable number of strong players competing, such as grandmasters. A "strong showing" refers to a player's high win ratio in a tournament. Opposite of weakness /weak, for example, a weak square.
1. A "strongpoint defense" means an opening which defends and retains a central pawn (White: e4 or d4; Black: e5 or d5), as opposed to exchanging the pawn and relinquishing occupation of that central square.
2. More generically, a strongpoint can be any square heavily defended.
Sudden death
The most straightforward time control for a chess game: each player has a fixed amount of time available to make all moves. See also Fast chess.
1. A ruse by which a player in a losing position tricks his opponent, and thereby achieves a win or draw instead of the expected loss. See also cheapo.
2. It may also refer more generally to achieving a win or draw from a clearly losing position.
Swiss tournament (see Swiss-system tournament)
This is a tournament that uses the Swiss system to determine player pairings. The basic idea is that every round each player is paired with an opponent with the same (or close to the same) score. The 33rd Chess Olympiad is an example of a Swiss tournament. See also round-robin tournament.
A symmetrical position on the chessboard means the positions of one's pieces are exactly mirrored by the opponent's pieces. This most often occurs when Black mimics White's opening moves. Black is said to break symmetry when he makes a move no longer imitating White's move.


Tabia (or Tabiya)
from Arabic طبيعة ṭabīʕa, "normal manner"
1. A position for the pieces from which a shatranj game was started: piece movement in shatranj was slow, hence games were possibly started from standard position, named Tabiyas, obtained by standard move sequences from the initial position.
2. As extension: the final position of a well-known chess opening. The position (e.g. the isolani) can be reached via different move sequences, even arising from different openings, and is usually considered prototypical in terms of strategic ideas.
3. (from 2) The opening position from which two players familiar with each others' tastes begin play.
See endgame tablebase.
A player who specializes in tactical play, as distinguished from a positional player.
Play characterized by short-term attacks and threats, often requiring extensive calculation by the players, as distinguished from positional play.
Used in casual games whereby both players agree to undo one or more moves.
Tarrasch rule
Named after Siegbert Tarrasch, this refers to the general principle that rooks usually should be placed behind passed pawns, either yours or your opponent's.
As abbreviation for tournament director.
An extra move, an initiative at development. A player gains a tempo (usually in the opening) by making the opponent move the same piece twice or defend an enemy piece. In the endgame, one may wish to lose a tempo by triangulation to gain the opposition. (Plural: tempos or tempi.)
Text move
This term is used in written analysis of chess games to refer to a move that has been played in the game as opposed to other possible moves. Text moves are usually in bold whereas analysis moves are not.
Theme tournament
A chess tournament in which every game must begin with a particular chess opening specified by the organizers, for example the Budapest Gambit (1.d4 Nf6 2.c4 e5).
Theoretical novelty (TN)
A new move in an opening. Also called simply a novelty.
A plan or move that, if left unattended, would result in an immediate depreciation of the opponent's position.
Threefold repetition
A draw may be claimed if the same position occurs three times with the same player to move, and with each player having the same set of legal moves each time (the latter includes the right to take en passant and the right to castle).
Tiebreaks (see Tie-breaking in Swiss-system tournaments)
This refers to a number of different systems that are used to break ties, and thus designate a single winner, where multiple players or teams tie for the same place in a Swiss system chess tournament.
Opportunities to make moves: similar meaning to tempo. A move that does not alter the position significantly is described as "wasting time", and forcing the other player to waste time is described as "gaining time".
Time control
The allowed time to finish a game, usually measured by a chess clock. A time control can require either a certain number of moves be made per time period (e.g., 40 moves in 2½ hours) or it can limit the length of the entire game (e.g., 5 minutes per game for blitz). Hybrid schemes are used, and time delay controls have become popular since the widespread use of digital clocks.
Time delay
A time control which makes it possible for a player to avoid having an ever-decreasing amount of time remaining (as is the case with sudden death). The most important time delays in chess are Bronstein delay and Fischer delay.
Time pressure (or Time trouble)
Having very little time on one's clock (especially less than five minutes) to complete one's remaining moves. See time control.
An abbreviation for theoretical novelty.
Top board
In team chess, the player who is assigned to face the strongest opponents. Also called first board. Second board faces the next strongest players, followed by third board, and so on. Generally board assignments must be made before the competition begins and players may not switch boards, although reserve players are often allowed as substitutes.
Slang for promotion.
Touched piece rule (or Touch-move rule)
The rule requiring a player who touches a piece that has at least one legal move to move that piece (and, if the player moves the piece to a particular square and takes his hand off it, to move it to that square). Castling must be initiated by moving the king first, so a player who touches his rook may be required to move it, without castling. The rule also requires a player who touches an opponent's piece to capture it if possible. A player wishing to touch a piece to adjust its position on a square without being required to move it signals this intent by saying "J'adoube" or "I adjust". This way of playing is common in official games, in favour of clock move.
Tata Steel Tournament 2013
A competition involving more than two players or teams, generally played at a single venue (or series of venues) in a relatively short period of time. A tournament is divided into rounds, with each round consisting either of individual games or matches in the case of knockout tournaments and team tournaments. The assignment of opponents is called pairing, with the most popular systems being round-robin and Swiss. Tournaments are usually referred to by combining the city in which they were played with the year, as in "London 1851", although there are well-known exceptions, such as "AVRO 1938".
Tournament book
A book recording the scores of all the games in a tournament, usually with analysis of the best or most important games and some background on the event and its participants. One well-known example is Bronstein's Zurich International Chess Tournament 1953. The less comprehensive tournament bulletin is usually issued between the rounds of a prestigious event, giving the players and world media an instant record of the games of the previous round. Individual copies may be bundled together at the conclusion of the event to provide an inexpensive alternative to the tournament book.
Tournament director (TD)
Organizer and arbiter of a tournament, responsible for enforcing the tournament rules and the Laws of Chess. Also tournament controller [chiefly British].

With 4...Nbd7 Black sets a trap in the QGD (1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5). White cannot win the d5-pawn due to the Elephant Trap.
See exchange.
To reach a position by transposition.
Arriving at a position using a different sequence of moves.
A move which may tempt the opponent to play a losing move. See also swindle.
A position of mutual zugzwang in which either player would lose if it is their turn to move.
A technique used in king and pawn endgames (less commonly seen with other pieces) to lose a tempo and gain the opposition.
Tripled pawns
Three pawns of the same color on the same file; generally considered a weakness due to their inability to defend each other.
Two bishops (or The two bishops)
Synonym for bishop pair.


This is a chess tactic (also known as removal of the guard) in which a defensive piece is captured, leaving one of the opponent's pieces undefended or underdefended.
Promoting a pawn to a rook, bishop, or knight instead of a queen. Rarely seen unless the knight can deliver a crucial check, or when promotion to a rook or a bishop instead of a queen is necessary to avoid stalemate.
United States Chess Federation (USCF)
This is a non-profit organization, the governing chess organization within the United States, and one of the federations of the FIDE.
Unorthodox opening
See irregular opening.
The act of breaking a pin. This allows the piece that was formerly pinned to move.
Antonym of sound.
An abbreviation for the United States Chess Federation.


Vacating sacrifice
A sacrifice made for the purpose of clearing a square for a different piece of the same color.
A move which opens one line and closes another.
See chess variant.
1. A sequence of moves or an alternative line of play, often applied to the opening. A variation does not have to have been played in a game, it may also be a possibility that occurs only in analysis.
2. The word Variation is also used to name specific sequences of moves within an opening. For an example, the Dragon Variation is part of the Sicilian Defence.
Vertical line
See file.


Waiting move
1. A passive but harmless move played while waiting for initiative from the opponent.
2. A move which carries no threat in and of itself but places the opponent in zugzwang.
An abbreviation for the World Chess Championship.
Weak square
A square that cannot be easily defended from attack by an opponent. Often a weak square is unable to be defended by pawns (a hole) and can be theoretically occupied by a piece. Exchange or loss of a bishop may make all squares of that bishop's color weak resulting in a "weak square complex" on the light squares or the dark squares.
An abbreviation for the Woman FIDE Master title.
An abbreviation for the Woman Grandmaster title.
White (see White and Black in chess)
1. The designation for the player who moves first, even though the corresponding pieces, referred to as "the white pieces", are sometimes actually some other (usually light) color. See also Black and first-move advantage.
2. Similarly, the light-colored squares on the chessboard are often referred to as "the white squares" even though they often are not literally white.
An extremely unclear or mind-bogglingly complicated position or move.
An abbreviation for the Woman International Master title.
1. A victory for one of the two players in a game, which may occur due to checkmate, resignation by the other player, the other player exceeding the time control, or the other player being forfeited by the tournament director. Chess being a zero-sum game, this results in a loss for the other player. An exception is a win as a result of a tournament bye.
2. See winning position.
A combination in which two pieces work together to deliver an alternating series of checks and discovered checks in such a way that the opposing king is required to move on each turn. It is a potent technique since on every other move, the discovered check may allow the non-checking piece to capture an enemy piece without losing a tempo. The most famous example is Torre–Lasker, Moscow 1925. Also called a seesaw.
The queenside a-, b-, and c-file, or the kingside f-, g-, and h-file. Also called flank.
Wing Gambit
The name given to variations of several openings in which one player gambits a wing pawn, usually the b-pawn.
Winning percentage
A number calculated by taking the percentage of games won by a player plus half the percentage of drawn games. Thus, if out of 100 games a player wins 40, draws 32, and loses 28, her winning percentage is 40 plus half of 32, i.e. 56 percent.
Winning position
A position is said to be a winning if one specified side, with correct play, can eventually force a checkmate against any defence (i.e. perfect defence). Also called a won game.
Woman FIDE Master (WFM)
A women-only chess title ranking below Woman International Master.
Woman Grandmaster (WGM)
The highest ranking gender-restricted chess title except for Women's World Champion.
Woman International Master (WIM)
A women-only chess title ranking below Woman Grandmaster and above Woman FIDE Master.
Won game
See winning position.
Slang for pieces. "A lot of wood came off the board" conveys that several piece exchanges occurred.
A weak chess player, also referred to as a fish, patzer or duffer. Colloquial, typically intended as criticism.
World Champion
A winner of the World Chess Championship.
Wrong-colored bishop (or Wrong bishop)
See wrong rook pawn.
Wrong rook pawn
With a bishop, a rook pawn may be the wrong rook pawn, depending on whether or not the bishop controls its promotion square.


X-ray attack
Also sometimes used in place of skewer.


[from German] See time pressure.
Zonal tournaments
Tournaments organised by the FIDE, the first qualifying cycle of the World Chess Championship. Each zonal tournament features top players of a certain geographical zone. The winners are then qualified for the interzonal tournament.
[from German] When a player is put at a disadvantage by having to make a move; where any legal move weakens the position. Zugzwang usually occurs in the endgame, and rarely in the middlegame.
[from German] A zwischenzug that is a check.
[from German] An "in-between" move played before the expected reply. In general, this involves responding to a threat by posing an even bigger threat to the opponent, forcing him to respond to the threat first.

Heterotopia is a concept in human geography elaborated by Foucault to describe places and spaces that function in non-hegemonic conditions. These are spaces of otherness, which are neither here nor there, that are simultaneously physical and mental, such as the space of a phone call or the moment when you see yourself in the mirror.

Foucault uses the term to describe spaces that have more layers of meaning or relationships to other places than immediately meet the eye. In general, a heterotopia is a physical representation or approximation of a utopia, or a parallel space that contains undesirable bodies to make a real utopian space possible (like a prison).

Foucault uses the idea of a mirror as a metaphor for the duality and contradictions, the reality and the unreality of utopian projects. A mirror is metaphor for utopia because the image that you see in it does not exist, but it is also a heterotopia because the mirror is a real object that shapes the way you relate to your own image.
He asked me Who is it that doesn't know how to conjugate draw? Of course me, but I answered... Do You know?, [Also practicing answering a question with another question.] It is not about conjugating, it's about all the different tenses, what do they mean and how they affect discourse.
Present perfect is an action realized in the past. I love the future perfect. The time when you know what you will be doing even if that is not possibly true, the conditional perfect progressive.
work through or edit out
Pataphysics is the science of imaginary solutions, which symbolically attributes the properties of objects, described by their virtuality, to their lineaments.

Pataphysics will examine the laws governing exceptions; pataphysics is patient; pataphysics is benign; pataphysics envies nothing, is never distracted, never puffed up, it has neither
aspirations nor seeks not its own, it is even-tempered, and thinks not evil; it mocks not iniquity: it is enraptured with scientific truth; it supports everything, believes everything, has faith in everything and upholds everything that is.

Pataphysics passes easily from one state of apparent definition to another. Thus it can present itself under the aspect of a gas, a liquid or a solid.

Pataphysics, the science of the particular, does not, therefore, study the rules governing the general recurrence of a periodic incident (the expected case) so much as study the games governing the special occurrence of a sporadic accident (the excepted case). … Jarry performs humorously on behalf of literature what Nietzsche performs seriously on behalf of philosophy. Both thinkers in effect attempt to dream up a “gay science”, whose joie de vivre thrives wherever the tyranny of truth has increased our esteem for the lie and wherever the tyranny of reason has increased our esteem for the mad.

A practitioner of pataphysics is a pataphysician or a pataphysicist.

The London Institute of Pataphysics has six departments:

Bureau for the Investigation of Subliminal Images
Committee for Hirsutism and Pogonotrophy
Department of Dogma and Theory
Department of Potassons
Department of Reconstructive Archaeology
The Office of Patentry
A clinamen is the unpredictable swerve of atoms that Bök calls “the smallest possible aberration that can make the greatest possible difference”. An example is Jarry’s merdre, a swerve of French: merde ("shit").

An antinomy is the mutually incompatible. It represents the duality of things, the echo or symmetry, the good and the evil at the same time. Hugill mentions various examples including the plus minus, the faust-troll, the haldern-ablou, the yes-but, the ha-ha and the paradox.

The syzygy originally comes from astronomy and denotes the alignment of three celestial bodies in a straight line. In a pataphysical context it is the pun. It usually describes a conjunction of things, something unexpected and surprising. Serendipity is a simple chance encounter but the syzygy has a more scientific purpose. Bök mentions Jarry suggesting that the fall of a body towards a centre might not be preferable to the ascension of a vacuum towards a periphery.

The absolute is the idea of a transcended reality.

An anomaly represents the exception. Jarry said that "pataphysics will examine the laws governing exceptions, and will explain the universe supplementary to this one". Bök calls it “the repressed part of a rule which ensures that the rule does not work”.

A pataphor is an unusually extended metaphor based on 'pataphysics. As Jarry claimed that pataphysics exists "as far from metaphysics as metaphysics extends from regular reality", a pataphor attempts to create a figure of speech that exists as far from metaphor as metaphor exists from non-figurative language.
some concepts
Let's get out of here
follow pages

Unlike then, than is not related to time. Than is used in comparative statements. EXAMPLES: ~Another pair of words that I see misused far more often than not is than and then. ~He is taller than I am. ~Other than the interest on a small inheritance, he had no income. ~Today's students certainly do seem to read less than students in previous generations did. ~We learned more on the playground than we did in the classroom. ~Despite their lack of flavor, the hothouse tomatoes cost far more than those from the farmers' market. THEN Then is used either as a time marker or with a sequence of events. EXAMPLES: ~I took all of the exams in the morning, and then I spent the rest of the day catching up on sleep. ~Back then we knew what was expected of us. ~I bought apples from this orchard last summer, but I seem to remember paying more for them then. ~Look over the study guide first, and then if you still have questions bring them up in class.
A quark (/ˈkwɔrk/ or /ˈkwɑrk/) is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.[1] Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can be found only within hadrons, such as baryons (of which protons and neutrons are examples), and mesons.[2][3] For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves.

There are six types of quarks, known as flavors: up, down, strange, charm, bottom, and top.[4] Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, top, and bottom quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators).

Quarks have various intrinsic properties, including electric charge, mass, color charge and spin. Quarks are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge. For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties have equal magnitude but opposite sign.

The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964.[5] Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968.[6][7] Accelerator experiments have provided evidence for all six flavors. The top quark was the last to be discovered at Fermilab in 1995.[5]

For some time, Gell-Mann was undecided on an actual spelling for the term he intended to coin, until he found the word quark in James Joyce's book Finnegans Wake:

Three quarks for Muster Mark!
Sure he has not got much of a bark
And sure any he has it's all beside the mark.
—James Joyce, Finnegans Wake[44]

Gell-Mann went into further detail regarding the name of the quark in his book, The Quark and the Jaguar:[45]

In 1963, when I assigned the name "quark" to the fundamental constituents of the nucleon, I had the sound first, without the spelling, which could have been "kwork". Then, in one of my occasional perusals of Finnegans Wake, by James Joyce, I came across the word "quark" in the phrase "Three quarks for Muster Mark". Since "quark" (meaning, for one thing, the cry of the gull) was clearly intended to rhyme with "Mark", as well as "bark" and other such words, I had to find an excuse to pronounce it as "kwork". But the book represents the dream of a publican named Humphrey Chimpden Earwicker. Words in the text are typically drawn from several sources at once, like the "portmanteau" words in "Through the Looking-Glass". From time to time, phrases occur in the book that are partially determined by calls for drinks at the bar. I argued, therefore, that perhaps one of the multiple sources of the cry "Three quarks for Muster Mark" might be "Three quarts for Mister Mark", in which case the pronunciation "kwork" would not be totally unjustified. In any case, the number three fitted perfectly the way quarks occur in nature.

Zweig preferred the name ace for the particle he had theorized, but Gell-Mann's terminology came to prominence once the quark model had been commonly accepted.[46]

The quark flavors were given their names for a number of reasons. The up and down quarks are named after the up and down components of isospin, which they carry.[47] Strange quarks were given their name because they were discovered to be components of the strange particles discovered in cosmic rays years before the quark model was proposed; these particles were deemed "strange" because they had unusually long lifetimes.[48] Glashow, who coproposed charm quark with Bjorken, is quoted as saying, "We called our construct the 'charmed quark', for we were fascinated and pleased by the symmetry it brought to the subnuclear world."[49] The names "bottom" and "top", coined by Harari, were chosen because they are "logical partners for up and down quarks".[36][37][48] In the past, bottom and top quarks were sometimes referred to as "beauty" and "truth" respectively, but these names have somewhat fallen out of use.[50] While "truth" never did catch on, accelerator complexes devoted to massive production of bottom quarks are sometimes called "beauty factories".[51]
Aphorism (from Greek ἀφορισμός aphorismos, "delimitation") is an original thought, spoken or written in a laconic (concise) and memorable form.[1] Aphorism literally means a "distinction" or "definition". The term was first used in the Aphorisms of Hippocrates. The oft-cited first sentence of this work (see Ars longa, vita brevis) is:
Life is short, art long, opportunity fleeting, experience deceptive, judgement difficult.
Mathematical analysis is a branch of mathematics that includes the theories of differentiation, integration, measure, limits, infinite series, and analytic functions.[1] These theories are usually studied in the context of real and complex numbers and functions. Analysis evolved from calculus, which involves the elementary concepts and techniques of analysis. Analysis may be distinguished from geometry; however, it can be applied to any space of mathematical objects that has a definition of nearness (a topological space) or specific distances between objects (a metric space).
noun: haven; plural noun: havens
a place of safety or refuge.
"a haven for wildlife"
synonyms: refuge, retreat, shelter, sanctuary, asylum, place of safety, place of security, port in a storm, harbour, oasis, sanctum
"a safe haven in times of trouble"
an inlet providing shelter for ships or boats; a harbour or small port.
synonyms: anchorage, harbour, port, mooring, roads; More

late Old English hæfen, from Old Norse hǫfn ; related to Dutch haven, German Hafen ‘harbour’.
1. The Symptom of Art (Pere-Version)

What is the relationship between the Symptom of Art and the Art of the Symptom. In the Twentieth Century, art took an entirely new direction, continually deconstructing its own form, reframing its own context, dissolving the boundary between presentation and re-presentation, and claiming its own sovereignty. Today this symptom appears to have reached its limits.
During the same period of modernity, a small movement within the field of medicine and psychiatry began to question the certainty of the symptom. Practices such as Psychoanalysis and Homeopathy have reinvented the field of medicine and disease. Picking up where the Greek Pharmakon and the Alchemical Magnum Opus left off, we are called upon to devise an Art of the Symptom for our times: an Autopoesis.
In a time where both the divine father and the nuclear father have dissolved, the pathway has been opened beyond neurosis toward psychosis and perversion. The art of the symptom is the construction of a "pere-version" or version of the father: a confrontation with the symbolic or social structure not as submission or rebellion but as intervention and invention. Creative destruction. Positive negation.

Dr. Scott Von, 2015

Dr Scott Von is a psychoanalyst and artist and Director of the New Clinic for Integral Medicine & Psychiatry in New York. He lectures and performs internationally on schizoanalysis and the symptom of art.
II. Schizoanalysis (Pulsion, Phantasm, Simulacrum)
Session by Dr. Scott Von, 24 April 2015 at 7.00pm

Art exists at the intersection of real, imaginary, and symbolic. It solicits the force of will and drive by deconstructing and reconstructing form. Art has forever been intertwined with the practice of magic and the politics of reality.

The sigil is an a-signifyng semiotic of powerful change. At the borderline of structural language and the suspension of the gaze in line, shape, and color exists the power to draw the drive into manifestation.

The indexical sign, or signal, releases the mana captured in rigid structures, dead forms, and stagnant dogmas. Black on white cuts through the imaginary hypnosis of personality and reference to lifeless archive, while sound and gesture crack the coding of a mechanistic matrix.

After a modern century of intense mana, the postmodern malaise of static representation threatens to suffocate our newborn vitality out of existence. This we cannot and will not have.

With this diagram we thus initiate the return of innovation and transformation. Being as Becoming. An ontology infinite and void. A topology of the continuous and discrete. A phenomenology of sovereignty. A schizoanalysis. A diagrammatology.

Dr. Scott Von, 2015

PMU palavras muito usadas
OW overused words
Moon Glossary: Lunar Terms and Definitions


Albedo — This term is a unit-less measure that refers to the how much an object diffusely reflects light from the sun.

Angular Diameter — The measurement of the diameter of a distant object from the perspective of the angle resulting between the observer and the object's outer edges. Also known as the 'visual diameter'.

Annular Eclipse — Refers to an solar eclipse where the Moon is between the Sun and the Earth, but with the Moon appearing smaller than the Sun to the observer, leaving a bright ring around the circumference of the Moon.

Anomalistic Month — The length of time that the Moon takes to pass between perigee (or apogee) passages — that is, the 27.55455 day period during which the Moon moves from its closest (or farthest) point to the Earth, all the way around and back again.

Anorthositic Rock — A calcium-rich rock type found in abundance on the Moon.

Aphelion — The farthest point from the Sun in a planetary body's orbit.

Apogee — The farthest point from the Earth in the Moon's orbit.

Apogean Tide — The name for low tide when the Moon is at it's farthest point from the Earth.

Apolune — The farthest point from the Moon in an object's orbit around it.


Basalt — Volcanic rock formed by rapidly cooling lava. Found on the moon and the earth.

Breccia — A type of rock that is composed of a matrix of different materials, minerals and fragments of other rocks. Found on the moon and the earth.


Celestial equator — The projection of the Earth's equator into space. It could be considered an invisible belt that surrounds the Earth in the minds of astronomers.

Celestial Mechanics — The specialized areas of astrology that describes the gravitational effects of heavenly bodies as well as their motion.

Colongitude — Also called selenographic colongitude, it is the longitude of the Moon's morning terminator.

Conjunction — The term applied when two planets are in close proximity to each other in the sky, from the perspective of an Earth-bound observer.

Crater Wall — The cliff-like wall formed by the impact of a meteor with a celestial body such as a planet or moon.

Crescent Moon — The famous image of the Moon frequently used in the media, consisting of only a thin crescent slice of the Moon being visible from Earth. This phase of the moon occurs just after the New Moon phase, which is also known as Dark of the Moon. There is also a Crescent Moon phase just prior to the next New Moon as well.


Dark of the Moon — So named because during this phase, the Moon is not visible in the sky, Dark of the Moon is also known as New Moon.

Declination — Declination is the position of a celestial body, such as the Moon, in the equatorial coordinate system. Declination is measured by degrees in relation to the celestial equator.

Diurnal — In astronomy, diurnal generally refers to the motion of an object in a 24 hour period. An example would be Moon-rise. These activities repeat every 24 hours. The diurnal arc describes the amount of time a celestial object takes to transition from fully risen to fully set.

DST — Daylight Savings Time.


Earthshine — The light of the sun that is reflected back into space by the Earth, and which can illuminate other objects such as the Moon.

Eclipse — Any interference between the light from the Sun and the object being illuminated. The Moon frequently moves between the Earth and the Sun, blocking out the Sun's rays.

Ecliptic — A term applied to the invisible path in the sky that the Sun moves through during the year, in relation to Earth and the other planets.

Elongation — The angle found between a planet and the Sun, from the perspective of the Earth.

Ephemeris — An astronomical text which contains the position of celestial bodies in the sky as seen from Earth at specific times. These positions are given in coordinates that astronomers can then use to locate and view these bodies.

Equatorial Tide — A tide with a period of 328 hours (approximately every two weeks) that occurs when the Moon is positioned above the equator.


Far Side — The side of the Moon which faces away from the Earth and which is not visible via planetary observation.

First Quarter Moon — During this phase of the Moon fifty percent of it is illuminated and visible from the Earth. It occurs after the Crescent phase and before the Waxing Gibbous phase.

Full Moon — During this phase of the Moon it is entirely illuminated and visible from the Earth. The Moon is opposite the Sun in this phase, with the Earth in between.


Gibbous Moon — There are two Gibbous phases of the Moon, with the first representing the growing moon between the First Quarter and the Full Moon and the second when it describes the Moon growing smaller as it shrinks down from the Full Moon to the Last Quarter. These phases are referred to as the Waxing and Waning Gibbous, respectively.

Gravity — Gravity is the attractive force which governs the motion of the celestial bodies. Gravity controls the orbits of all planets in our solar system as well as our solar system's relative motion to the Universe. It also plays a significant role in the distribution of mass throughout the Universe.

Grazing Occultation — A phenomenon in which the varied topography of the Moon's surface causes stellar objects such as stars to disappear and reappear at the northern or sudden limit of the Moon intermittently. This occurs due to the motion of the Moon itself across the path between a certain patch of the heavens and the Earth.

Greenwich Mean Time — Time derived from the annual average movement of the sun over the zero degrees longitude position of the Greenwich Observatory in England. The mean is used in order to compensate for the Sun's non-uniform motion. It has since been replaced in astronomical circles by Universal Time.


Half Moon — Term that is used to describe the First Quarter Moon and the Last Quarter Moon.


Intercalation — The source of leap years, or the addition of an extra day or other period of time in order to reconcile the solar year with that of the calendar we use. This is necessary because the solar year contains approximately 365.25 days, making it necessary to add a full extra day to the calendar every four years. In the past, much longer periods of time were used during intercalation. Intercalary days or months can also be added to the lunar calendar.


Lacus — Areas on the Moons surface that have the topography of lakes are prefaced with this Latin term for lake.

Last Quarter — The phase of the Moon between the Waning Gibbous and the Waning Crescent, where fifty percent of the Moon is still visible before the Waning Crescent phase wipes it from the sky.

Latitude — Coordinate system used on a planetary body to give the location of a point in relation to its equator. There are ninety degrees of latitude north and south of the equatorial line.

Librations — The gentle rocking motion of the Moon as it orbits the Earth that allows observation of the side that normally faces away from our planet. In total, through this irregular motion fifty-nine percent of the Moon can be seen.

Limb — The outermost edge of a planetary body or celestial object.

Longitude — Coordinate system used on a planetary body to give the location of a point in relation to a reference meridian. Meridians are lines drawn by cartographers and astronomers that pass through the northern point on the horizon, meeting at the celestial pole. As there is no natural starting meridian, the base or center meridian is chosen arbitrarily on each planet or moon. On Earth's Moon, Sinus Medii represents the zero degree point for longitude, with ninety degrees of longitude available to the east and west.

Lunar Day — There are two definitions of this term. The first refers to the period of time it takes for the Moon to spin completely on its axis in terms of its position to the sun. The second is the amount of time it takes for the Moon to complete a single orbit around the Earth. Due to the eccentric orbit, a Lunar Day varies in length. Lunar Eclipse — This event occurs when the Full Moon moves through the shadow cast by the Earth as it passes between the Sun and the Moon.

Lunar Interval — The difference in time between a phase of the Moon or tide occurring at the Greenwich meridian and a local meridian. This interval represents the passage of the Moon during this time.

Lunar Rays — Lines scored into the crust of a celestial body caused by mass ejected on impact from a meter. Found on both the Moon and Mars.

Lunitidal Interval — The period of time that occurs between the Moon passing over a point on Earth and the next high tide for that point.


Magnitude — The brightness of a celestial body. A lower magnitude number indicates a brighter object.

Mare — Name given to plains composed of basalt on the Moon. From the Latin word for 'sea', so-called due to their large landmass. These basalt deposits were left by the eruptions of now-extinct volcanoes.

Mascon — A region in the crust of a celestial body which is denser than average and as such acts to create a local gravitational anomaly. On the moon, there are several basins which demonstrate these properties.

Meridian — Meridians are lines drawn by cartographers and astronomers that pass through the northern point on the horizon of a planetary body or moon, meeting at the celestial pole.

Meteoroid — A meteoroid is any body drifting in space that has a large enough mass to be detected but which is significantly smaller than an asteroid. The exact limit at which a meteoroid is reclassified as an asteroid is up for debate, but generally, any object smaller than 50 meters in diameter is considered a meteoroid.

Moon — The natural satellite in orbit around the planet Earth. Also the classification for any natural satellite found in orbit around any other planet.

Moon Rise — Similar to sunrise, it is the first appearance that the Moon makes over the Earth's horizon, and as such it is relative to the geographical position of the observer.

Moon Set — The opposite of Moon Rise, it is the when the Moon disappears behind the Earth's horizon, relative to the observer.


Nadir — The point with a negative ninety degree inclination in relation to the observer, or the point directly beneath their feet.

Neap Tide — When the Moon is at its First Quarter or Last Quarter, its forces are partially cancelled out by the Sun. This leads to a lower high tide than normal.

Near Side — The side of the Moon that is visible from the Earth.

New Moon — If the Moon is on the same side of the Earth as the Sun, then the face of the Moon that can be seen from the Earth is no longer illuminated by the Sun's rays — as only the opposing side is facing the Sun. As a result, it is invisible in the Earth's sky.

Nodes — Also called Lunar Nodes, these are the points where the orbit of the moon intersects the path of the Sun in terms of how it appears to move against the stars. This solar path is called the ecliptic.

Nodical Month — A period of 27.212220 days representing the movement of the Moon starting and finishing at a specific Lunar Node.


Occultation — The act of one celestial body obscuring another as a result of moving between the observer and the object being observed. The most well known occultations are the lunar and solar eclipses.

Old Crescent Moon — Phase of the Moon that occurs between the Last Quarter and the New Moon. In this phase, the Moon is visible only as a very thin crescent.

Opposition — The term used to describe two celestial bodies as being opposite each other in the sky, relative to the observer. An example is when the Moon is opposite the Sun, with the observer on the Earth in the middle.

Orbital Eccentricity — Objects orbit in an elliptical fashion; eccentricity can be thought of as the amount by which the orbit of a celestial body deviates from a circular shape.


Palus — A Latin term meaning 'swamp' that is used to describe topographical features on the moon which resemble dark plains or swamps.

Parallax — The apparent motion of an observed object against the background caused by the movement of the observer. An example of this is the motion of the stars as seen from observatories on Earth.

Partial Eclipse — When a celestial body gets between another object and a light source, it casts 2 shadows. The umbra blocks all of the light from the light source (usually a sun), and the penumbra blocks only a portion of that light. A partial eclipse occurs when an object finds itself in the penumbra.

Penumbra — The name given to the shadow cast by a celestial object that only blocks a portion of the light.

Perigee — The closest point to the Earth in the Moon's orbit.

Perigean Tide — The tide that occurs when the moon is at its closest point to the earth during its orbit. These tides are higher than normal.

Perihelion — The closest point to the Sun in a planetary body's orbit.

Perilune — The closest point to the Moon in an object's orbit around it.

Phases — When applied to the Moon, the phases refer to the different illumination that it undergoes during it's orbit around the Earth and the Sun. The most commonly known phases of the Moon include Full Moon and the Quarter Moon.


Quadrature — Term that describes two celestial bodies appearing to be ninety degrees apart, from the perspective of the observer. An example is when the Moon appears to be at a right angle to the Sun, as viewed from Earth.


Radius — Half the diameter of any sphere or circle.

Regression of nodes — The westward movement of the nodal points of the Moon's orbit where it intercepts the orbit of the sun, also known as the elliptic.

Revolution — A way to describe the movement of one celestial body as it orbits another. A complete revolution is a complete orbit.

Rille — Grooves in the Moon's surface which resemble canals or canyons.

Rotation — The motion of a sphere which is spinning around its own axis. An example would be a basketball spinning on the tip of a finger.


Saber's Beads — Detached points of light seen along the limb of very young and old lunar crescents. The striking resemblance to 2nd and 3rd contacts during a total solar eclipse was first noted by American astronomer Stephen Saber.

Saros Cycle — This cycle predicts the occurrence of eclipses, as after a period of 18 years and 11.3 days the Earth, Moon and Sun all line up in the formation necessary to generate this celestial event.

Satellite — Any object that orbits another celestial body.

Selenography — The study of the topography and features of the Moon's surface.

Sidereal Month — Period of 27.32166 days which represents the Moon's movement through space relative to a start point amongst the stars.

Sinus — Latin term that describes topographical features of the moon that resemble bays.

Solar Eclipse — Term that describes when the Sun is obscured by the Moon from the perspective of Earth.

Spring Tide — When the conjunction or opposition of the Sun, the Earth, and the Moon occurs, approximately at the times of the Full Moon and the New Moon, the Sun acts to augment the tidal forces of the Moon, creating a higher than normal tide.


Tektites — Objects made from natural glass that are created from the impact of meteorites. They can be found on the Earth and the Moon.

Terminator — The line which delimits night (shadowed portion) and day (sunlit portion) on a celestial body. The Moon's phases illustrate this.

Tides — The rising and falling levels of the ocean in comparison with the bodies of land on Earth. Tides are the result of the gravitational forces of the Sun and the Moon acting upon the planet.

Transit — The movement of a celestial body across another, from the viewpoint of an observer.

Tropical Month — The period of time, (27.321582 days ), that it takes for the Moon to return to a specific celestial longitude (its position in reference to the stars).


Umbra — The name given to the shadow cast by a celestial object that entirely blocks out illumination.


Waning Moon — The term used to describe the period of the Moon as it moves from a Full Moon to a New Moon, decreasing in visibility with respect to an Earth-bound observer.

Waxing Moon — The term used to describe the period of the Moon as it moves from a New Moon to a Full Moon, increasing in visibility with respect to an Earth-bound observer.

X, Y, Z

Young Crescent Moon — Name for the initially visible crescent of the Moon immediately after the New Moon.

Zenith — The point with a ninety degree inclination in relation to the observer, or the point directly above them.