Chess Glossary

The quality of a chess position that describes mobility or freedom of movement for pieces. An active piece is more likely to have a positive influence in the outcome of a game than an inactive piece (a cramped, blocked, or undeveloped piece). Activity is a key quality of a chess position.

An over-the-board game may be adjourned when it is not concluded in one session. When a game is adjourned, one of the players seals his next move in an envelope to keep it secret. The sealed move is opened when the game resumes at a designated later time. Adjournments are rare in modern times, because of a desire by most tournament organizers to conclude even the longest games in one session. The rate of play required by many international tournaments is 40 moves in two hours, followed by 20 moves in one hour, and then half an hour extra for the rest of the game. The third and last part of this time control is known as sudden death, and does not require adjournment.

A term used to describe the winning potential of one side or color in a game of chess usually based on the position of chess pieces on the board. When one side or color in a game of chess is winning the game, then that side is said to have the advantage, edge, pull, or plus. For example, a "clear advantage" (edge, pull, or plus) is enough to win with correct play, whereas a "slight edge" just offers better practical chances even though the players might draw the position with best play. A judgement of an advantage must consider complex criteria such as material (more pieces or pawns), space (more room to maneuver), activity (more influence of pieces), king safety (one side has a safer king than the other), or other weaknesses (backward pawn, etc.).

The most popular modern chess notation used to record the moves of a chess game. It is called this because of the unique way it identifies each square of an 8 by 8 matrix chess board. Each column or file is labeled with a letter. Each row or rank is labeled with a number.

A coordinated attempt to gain an advantage in a game of chess by means of aggressive play. The primary objective in most attacks is to checkmate an opponent’s king, because of the king's very high value. A well executed attack often forces one's opponent to sacrifice material in defense, or accept weakness leading to an advantage for the attacking side.

A pawn that cannot be protected by pawns on its flanks, because they have advanced too far ahead of it. A backward pawn is consider a fundamental weakness in a chess position because it can be attacked. Its defense requires pieces that are better employed in other plans. See also isolated pawn.

A bishop whose mobility is reduced usually by friendly pawns on the same colored squares. Any ineffective bishop.

If both bishops on the same side survive late into a game of chess, then their value is enhanced for two reasons. Together they can attack a piece on any color square. Their mobility is usually less restricted by pawns late in the game. Therefore, a bishop pair is a notable advantage.

An expert player plays one or more opponents without sight of the board.

A fast game of chess usually clocked in 5 or 10 minutes.

A term that describes the situation where the advance of a pawn is prevented by an opponent's piece directly in front of the frustrated pawn.

A term used to describe a piece whose mobility is limited by the physical presense of another piece often of the same color. Specific positions that involve blocked pieces include discovered check, double check, and blockade.

A bad move. A mistake that overlooks a simple tactical response. See also howler.

To precisely work out a series of moves considering potential replies.

The four squares in the middle of the board.

A clever tactical combination or trap usually made by a losing side to hold a draw or even win.

Any position where a King cannot avoid capture. The objective end of a chess game.

A term used to describe a position where pawns block the mobility of the pieces around some or all of the board. The opposite of an open position.

A tactical exploitation of a position (forced set of moves) beginning with a material sacrifice that leads to an advantage (usually a gain of material and/or a better position) for the initiator of the moves.

The quality of a chess position that inhibits mobility or freedom of movement for pieces behind pawns of the same color. A cramped position lacks space. When a player's position is judged to be cramped, then that player has less freedom of maneuver than his opponent. A player that is cramped cannot switch the play from one side of the board to the other as quickly as his opponent. A cramped position is one key quality in assessing a chess position.

The process of moving pieces from their original squares to positions where they can better aid the player's plans.

A phrase used to describe an often powerful move where a line is opened allowing an otherwise blocked piece to give check to the enemy king. If the moving piece also gives check, then the move is described as a double check.

A phrase used to describe the number of positions or ply in a tablebase between any given endgame position and a conversion of material. A conversion of material may be either a promotion or capture. Such conversions often indicate a major shift of endgame advantage.

A phrase used to describe the number of positions or ply in a tablebase between any given endgame position and checkmate.

A special case of discovered check where the moving and discovering piece also gives check - leading to two pieces giving check simultaneously. The king must then move because no other means is available to extricate the king from this special case of check by two pieces simultaneously.

Two pawns of the same color on the same file. Generally considered a disadvantage because the pawns cannot defend each other.

English word for what the Americans call the game of checkers.

A common result in a game of chess when neither side wins or loses. A draw may result when neither side has sufficient material to force a win, or agreement of both players, or stalemate, or etc.

The probability in any complex and roughly equal position that one or both sides may successfully draw a game of chess. The game of chess is extremely complex. Neither humans or machines can determine with certainty the outcome of a game when given a complex position. However, skilled and experienced players can often estimate the probability that one side can win, lose, or draw the game. Such an estimate is based on an understanding of sometimes subtle criteria such as board position, player skills, time pressure, and strategy both on the board and off. Usually, winning, losing, and drawing chances are judged as either good or poor. If a position is sufficiently unclear that either side may win, lose, or draw, then that position is estimated to give both sides equal chances.

Any chess game position from which a draw must result from accurate play. Many complex drawn positions may still offer winning chances for one or both sides with alert play. The phrase "drawn position" is rarely used by experienced players to mean an artistically rendered, or randomly selected position. It is unknown whether the starting position is also a drawn position.

The Encyclopedia of Chess Openings is a collection of texts detailing the moves of common chess opening lines with commentary. Common opening lines are classified by a de facto standard ECO code such as B01 (Center Counter Game or Scandinavian Defense). Here is a list of ECO codes.

A numerical measure of a chess player's strength. The rating system or algorithm was named for its inventor Professor Elo. The system in some form is used by most major chess organizations. A casual player may be rated below 1200, a beginner to competitive play about 1400, a strong club player around 1800, a typical Master around 2300 and a Grandmaster above 2500. World Class players commonly achieve ratings above 2600. Some strong Grandmasters earn a rating in excess of 2700. Only a few players in history are rated above 2800.

Also called ending. It is the third and final phase of the game after the opening and middlegame. An endgame is entered when each player has relatively few pieces remaining on the board. Kings often become active pieces in an endgame because other pieces (especially the queens) are usually no longer around to attack them. The promotion of pawns to get more pieces is a common goal in the endgame.

A French phrase commonly used by English-speaking players that means in passing. A pawn capture where a pawn on the 5th row captures an opponent's pawn on an adjacent file which has just move 2 squares forward on its first move as if it had moved only one square. This complex rule was created to prevent a pawn from using the two-square first-move rule to pass an opponent's pawn and avoid capture.

A French phrase commonly used by English-speaking players that means in prison. Said of an undefended piece that can be captured. A piece en prise is often the result of a blunder. See also lost position.

Extended Position Description is a standard for describing chess positions along with an extended set of structured attribute values using the ASCII (American Standard Code for Information Interchange) character set. It is intended for data and command interchange among chess playing programs. It is also intended for the representation of portable opening library repositories. The first four fields of the EPD specification are the same as the first four fields of the closely related FEN specification. Like FEN, EPD can also be used for general position description. However, unlike FEN, EPD is designed to be expandable by the addition of new operations that provide new functionality as needs arise. A text file composed exclusively of EPD data records should have a file name with ".epd" as the suffix. More information can be found at this site.

A common intermediate result in a game of chess that either side may win, lose, or draw.

The same probability that either player of any complex chess position may win, lose, or draw. The game of chess is extremely complex. Neither humans or machines can determine with certainty the outcome of a game when given a complex position. However, skilled and experienced players can often estimate the probability that one side can win, lose, or draw the game. Such an estimate is based on an understanding of sometimes subtle criteria such as board position, player skills, time pressure, and strategy both on the board and off. Usually, winning, losing, and drawing chances are judged as either good or poor. If a position is sufficiently unclear that either side may win, lose, or draw, then that position is estimated to give both sides equal chances.

Any chess game position from which a player can win, lose, or draw. Equal positions offer equal chances for both sides with alert play.

The word "exchange" without amplifying verbage means a simple trade of pieces of identical value. However, the presense of amplifying verbage signifies an unequal trade; most often the advantage of a rook for a bishop or knight. If you have a rook and your opponent has a less valuable bishop, you are said to have "won the exchange". You are "up an exchange" or an "exchange ahead." Likewise, "sacrificing the exchange" is giving up a rook for a less valuable knight or bishop.

Non-orthodox chess problem compositions. A problem or puzzle where some official rules of the traditional game of chess are suspended or changed.

Forsyth-Edwards Notation is a standard for describing chess positions using the ASCII (American Standard Code for Information Interchange) character set. It is intended as a standard position notation for chess programmers, for page layout programs, and for confirming position status for e-mail competition. Six FEN fields specify the piece placement, the active color, the castling availability, the en passant target square, the halfmove clock, and the fullmove number. The first four fields of the FEN specification are the same as the first four fields of the closely related EPD specification. Like FEN, EPD can also be used for general position description. However, unlike EPD, FEN is not as expandable. FEN provides no means to add new operations that provide new functionality as needs arise. A text file composed exclusively of FEN data records should have a file name with ".fen" as the suffix. More information can be found at this site.

A chess position that evolves by developing a bishop onto a long diagonal; specifically on the b2 and/or g2 squares. The position is considered very strong because the bishop exerts maximum pressure on its longest diagonal. A word derived from the Italian word fianco meaning flank.

Federation International des Echecs, one of the international governing bodies of chess.

A vertical (up and down) row of squares. The players' Kings start the game on the same file.

A bad chess player.

A move or set of moves that are required (forced) to avoid a lesser game result.

The name given to the fastest possible mate: 1.f4 e6 2.g4 Qh4#. It is so named because white must play foolishly to allow this mate. Other similar foolish lines of play are also justly known as fool's mate. See also scholar's mate.

A tactical concept when a piece attacks two or more opponent pieces simultaneously.

A chess position that cannot be effectively attacked or broken down even with superior material advantage.

A speculative sacrifice of material for compensation such as an advantage. A gambit usually involves the sacrifice of a pawn or minor piece when a game is in a complex phase such as the opening or middlegame. A gambit is difficult, but possible to refute. An apparent sacrifice of material for a clear advantage is called a combination; not a gambit.

An outstanding and highly rated chess player.

A helpmate is a composed chess problem where both sides cooperate to allow white to mate black. Black moves first. Helpmate problems are a form of fairy chess.

An informal word for a knight. The term is used most often by children.

A bad move. A mistake that overlooks a simple tactical response. See also blunder.

Control of the game, usually due to better placement of men and easier access to weaknesses in the opponent's position.

Any computer that enables live chess play between remote (usually) players, and is connected to the Internet. There are many Internet Chess Servers.

A pawn that cannot be protected by pawns on its flanks, because they were captured. An isolated pawn is consider a fundamental weakness in a chess position because it can be attacked. Its defense requires pieces that are better employed in other plans. See also backward pawn.

A French word commonly used by English-speaking players that means I adjust. A notice to one's opponent that one is about to adjust the position of a piece on its square with no intention to move the piece to another square.

Observing and commenting on a chess game, usually in a manner that disturbs the players.

A common result in a game of chess when the losing side is checkmated or resigns before checkmate. A lose may result when a player makes the last mistake or blunder.

The probability in any complex and roughly equal position that one side may successfully lose a game of chess by thoughtless play. The game of chess is extremely complex. Neither humans or machines can determine with certainty the outcome of a game when given a complex position. However, skilled and experienced players can often estimate the probability that one side can win, lose, or draw the game. Such an estimate is based on an understanding of sometimes subtle criteria such as board position, player skills, time pressure, and strategy both on the board and off. Usually, winning, losing, and drawing chances are judged as either good or poor. If a position is sufficiently unclear that either side may win, lose, or draw, then that position is estimated to give both sides equal chances.

Any chess game position from which a player must lose with accurate play. Many complex lost positions may still offer winning or drawing chances with alert play. It is unknown whether the starting position is also a lost position.

Short for checkmate, when a King cannot avoid capture.

A common chess problem where white on the move must checkmate black in two moves despite black's best reply. Mate in three, four, or more moves are also common training exercises.

The chess pieces. The player whose remaining pieces are of greater value is said to have a material advantage. Material is one key quality in assessing a chess position.

The second phase of the game after the opening and before the endgame, in which development of the pieces is complete or nearly complete and many pieces are captured or traded as the players pursue their creative plans.

An advance of a minority of pawns towards a greater number of enemy pawns. The objective of a minority attack is to create a isolated pawn weakness in the enemy position.

A term used to describe a position where pawns do not block the mobility of the pieces around some or all of the board. The opposite of a closed position.

The first phase of the game before the middlegame and endgame, in which players try to rapidly develop their pieces, gain room for their pieces to maneuver, and on bringing their kings to safety. Many promising opening lines of play are analyzed and documented extensively in texts and computer databases.

Bishops can only move on one color square determined by their original position. Thus we have light- and dark-colored squared bishops. If only two opposing bishops on opposite colored squares are captured from the board, then opposite colored bishops remain. (See also bishop pair.) The opposite colored bishops characterize chess play as asymetrical. The opposite colored bishops cannot challenge or capture each other. Therefore, the attacking side often has the advantage in a middlegame with opposite colored bishops. However, opposite colored bishop endgames are often drawn, because neither site can control both colored squares to force the advance of a pawn.

A term used to describe two kings, usually in an endgame, that are positioned near each other such that they prevent or block each other's progress.

A square that supports a piece. The square is usually in the opposite side of the board from the piece's origin; in the enemy's camp. The square is usually protected by a least one pawn.

A terms that refers to chess play over a chess board as opposed to postal or email chess.

One type of advantage in chess where a pawn's progress is not guarded or blocked by enemy pawns on the flank or in front of it.

A bad chess player.

Portable Game Notation is a standard designed for the representation of chess game data using ASCII text files. PGN is structured for easy reading and writing by human users and for easy parsing and generation by computer programs. A text file composed exclusively of PGN data records should have a file name with ".pgn" as the suffix. More information can be found at this site.

A tactical concept when a piece cannot or should not move because it shields another piece from capture. The shielding piece is said to be pinned to the shielded piece.

A method or line of play designed to improve a position. A chess player should always have a plan. Your plan often lasts only as long as it takes for your opponent to make a move.

White or black's move. Exactly one half of one complete move pair.

The arrangement of chess pieces. The player whose pieces have better placement is said to have a "positional advantage."

When a pawn reaches the eighth (last) rank, the player must replace it with his choice of a queen, rook, bishop, or knight. Thus if a pawn survives to reach the eighth rank, then it is rewarded by promotion to a piece of higher value.

A special case of pawn promotion to a queen. This phrase is often used to describe promotion in general, because a pawn is usually promoted to a queen; the highest valued option.

A horizontal (left to right) row of squares. The pawns start the game on each player's second rank.

A score, usually numerical, of a player's ability.

A deliberate loss of material for anticipated advantage. Also known as sac.

The name given to an attack that leads to an early mate like: 1. e4 e5 2. Bc4 Nc6 3. Qh5 Nf6 4. Qxf7#. The attack is easily refuted, and therefore rarely attempted except against beginners. Other similar lines of play are also justly known as scholar's mate. Scholar's mate requires more coordination in the attack than fool's mate.

A method of secretly recording the next move of an adjourned game (an unfinished game) until play is resumed.

When one person plays chess with two or more opponents at the same time.

A tactical concept when a piece attacks two or more enemy pieces on a row (with a rook or queen) or diagonal (with a bishop or queen).

The quality of a chess position that permits greater mobility or freedom of movement for pieces behind pawns of the same color. Space is the opposite of cramped. When a player's position is judged to have more space, then that player enjoys greater freedom of maneuver than his opponent. A player that enjoys more space can switch the play from one side of the board to the other more quickly. Space is one key quality in assessing a chess position.

A phrase used to describe a type of checkmate by a knight where the king has no escape, because its own pieces block all escape routes.

A drawn game when a no legal move is possible.

A term used to describe a general thought process used to plan a game of chess. Strategy is more concerned with distant future moves than the calculation of tactics for the next move.

A term used to describe a composed endgame position where very artful play and a lot of thought (study) is required to win or draw. Commentators often refer to a game position as a study if it is unusually difficult and artistic.

A time period in a game of chess in which all remaining moves must be completed. The rate of play required by many international tournaments is 40 moves in two hours, followed by 20 moves in one hour, and then half an hour extra for the rest of the game. The third and last part of this time control is known as sudden death, and does not require adjournment.

A computer database of endgame positions (calculated by retrospective analysis) designed to enable perfect play from any position. Currently tablebases are limited to positions of 7 or fewer pieces. Tablebases come in two content types; Distance to Mate (Eugene Nalimov, Steven J Edward), and Distance to Conversion (Ken Thompson). Current tablebases range from 8Gb compressed to 30Gb uncompressed. The Nalimov tablebase is most popular because it is efficient, nonproprietary, compressed, and most complete (ignoring only uncastled positions which are very unusual in the endgame).

A term used to describe a short-term sequence of moves involving threats and counter threats.

A turn at move. Chess time as opposed to clock time. A slight initiative or advantage in time to pursue one's plans. Sometimes called a ply or half-move in computer chess terminology. The characteristic rate or rhythm of the game of chess.

A term used to describe a time limit for a chess player to complete some number of moves.

A phrase used to describe the difficulty faced by a player who must complete a disproportionate number of moves before a time-control.

A term used to describe pawn promotion to any piece other than a queen. A player may choose to under-promote his pawn to gain advantage, or avoid stalemate.

United States Chess Federation, one of several American governing bodies of chess.

A sequence of moves, or line of play. There are many variations (possible moves) in a game of chess.

Any non-threatening move that attempts to gain the advantage because one's opponent now must move.

A flaw in a position. An isolated or blockaded pawn, lack of space, bad bishop, or any other positional flaw that increases losing chances are examples of weaknesses.

A common result in a game of chess when the winning side checkmates or accepts the resignation before checkmate of his opponent. A win may result when a player makes the second to the last mistake or blunder.

The probability in any complex and roughly equal position that one side may successfully win a game of chess with alert play. The game of chess is extremely complex. Neither humans or machines can determine with certainty the outcome of a game when given a complex position. However, skilled and experienced players can often estimate the probability that one side can win, lose, or draw the game. Such an estimate is based on an understanding of sometimes subtle criteria such as board position, player skills, time pressure, and strategy both on the board and off. Usually, winning, losing, and drawing chances are judged as either good or poor. If a position is sufficiently unclear that either side may win, lose, or draw, then that position is estimated to give both sides equal chances.

Any chess game position from which a player must win with accurate play. Many complex winning positions may still offer losing or drawing chances with alert play by one's opponent. It is unknown whether the starting position is also a winning position.

A comment about a chess game not intended for the players. A command commonly used by spectators to comment on a chess game played on the Internet via remote computers.

A bad chess player.

A German word commonly used by English-speaking players that means a compulsion to move. When a player would rather maintain the current position, but must move in turn.

A German word commonly used by English-speaking players that means an in-between move. Any move made prior to an apparently forced move.