Chess terms: Rules, notation and equipment
50 terms about rules and notation, each with a plain definition and links to related terms.
Adjusting a piece means straightening one on its square; the Laws allow it only to the player on the move, who must first say "j'adoube" or "I adjust" to show they do not intend to move it.
Algebraic notation is the standard system for recording chess moves, naming each square by file letter and rank number and each move by the piece letter and destination square, as in Nf3 or exd5.
Annotation symbols are the short marks added to written moves, such as + for check, # for checkmate, x for a capture and (=) for a draw offer, along with commentators' marks like ! and ?.
The arbiter is the official who sees that the Laws of Chess and the rules of the event are followed, rules on disputes and claims, and can penalize rule breaches during a tournament.
The bishop moves any number of squares along a diagonal, as long as no piece stands in the way, so each bishop stays on one color of square for the entire game.
A capture happens when a piece moves onto a square held by an enemy piece, which is removed from the board as part of the same move; the king can be attacked but is never captured.
Castling is a special king move that shelters the king and activates a rook in one turn: the king goes two squares toward an unmoved rook, which then jumps to the king's other side.
Check is the state of a king that stands attacked by one or more opposing pieces; the player whose king it is must end the attack with the very next move, because no legal move may leave one's own king attacked.
Checkmate, or mate, ends a chess game at once: the king of the side to move is under attack, and none of that side's legal moves can remove the attack, so the player who delivered it wins.
A chess clock is a pair of linked timers of which only one runs at a time; after each move a player presses their side to stop their own time and start the opponent's.
Chess pieces are the sixteen units each side starts with: one king, one queen, two rooks, two bishops, two knights and eight pawns; in everyday speech, though, piece usually means everything except the pawns.
Chess960 is a variant that begins from one of 960 randomly chosen back-rank setups, with the king between the rooks and the bishops on opposite colors, and is otherwise played with the usual rules.
The chessboard is the playing field for every game of chess, a large square divided into eight rows and eight columns of light and dark cells that alternate, set so the corner nearest each player's right hand is light.
Coordinates are the letters a to h along the files and the numbers 1 to 8 along the ranks that give every square of the chessboard a unique name, such as c3 or g7.
A dead position is one in which checkmate can no longer happen for either side, however the moves go and however cooperative the players are, and the game ends as a draw the moment it arises.
Descriptive notation is the older system that records moves relative to each side's own pieces and ranks, such as P-K4 or N-KB3, and it has been largely replaced by algebraic notation.
A diagonal is the slanting path a bishop travels, a straight run of squares of a single color from one edge of the board to a neighboring edge, also used by the queen and by a pawn when it captures.
Disambiguation is the extra letter or number added to a written move when two identical pieces can move to the same square, such as Nbd2 or R1e2, so the move reads only one way.
A draw by agreement ends the game with a half point each when both players settle on a draw, which the Laws allow once each has made a move unless the rules of the event restrict it.
A draw offer is a proposal to end the game in a draw; under the Laws it is made after you move and before you press your clock, carries no conditions, and cannot be withdrawn once made.
En passant is a pawn capture that exists for one move only: after an enemy pawn leaves its starting square by two steps and stops beside your pawn, you may take it by moving to the square it skipped.
FEN is a compact line of text that records a chess position: the pieces rank by rank, whose turn it is, castling rights, any en passant square, and two move counters.
The fifty-move rule lets the player on move claim a draw once fifty moves by each side have been completed with no pawn move and no capture, so a game that makes no progress cannot run on forever.
A file is one of the eight vertical columns of the chessboard, labeled a to h from White’s left to right, and a key line along which rooks, queens and pawn structures operate.
Fivefold repetition is the rule that a game is drawn automatically, with no claim needed, once the same position has appeared at least five times.
Flagging is winning, or claiming to win, on time because an opponent's clock has run out; the flag-fall loses the game unless the other side could never checkmate.
A forfeit is a loss awarded without a finished game, for example when a player arrives after the default time, persistently refuses to follow the Laws, or has an unapproved electronic device in the playing venue.
A half-move, also called a ply, is a single turn by one side, so a full move in chess notation consists of two half-moves, one by White and one by Black.
An illegal move is one that breaks the rules of how a piece moves or leaves your own king in check; in over-the-board play it is corrected, and a second completed illegal move loses the game.
Insufficient mating material describes a position in which neither side has enough pieces to deliver checkmate by any legal sequence, which the Laws treat as a dead position and a draw.
The king moves one square in any direction or castles, may never be left in check or moved into check, and is never captured, because the game ends when it is checkmated.
Kingside castling is a move in which the king steps two squares toward the h-file rook and that rook jumps to the square the king crossed, written 0-0 or O-O in notation.
The knight moves to one of the nearest squares that is not on its own rank, file or diagonal, an L-shaped jump, and it is the only piece that can leap over other pieces.
Long algebraic notation is the fuller form of algebraic notation in which each move lists its square of departure as well as its square of arrival, so the knight move Nf3 becomes Ng1-f3 and the pawn move e4 becomes e2-e4.
The pawn moves one square straight forward, or two from its starting square, captures one square diagonally forward, and is exchanged for a queen, rook, bishop or knight on the far rank.
PGN is a text-file standard for chess games: header tags name the event, players and result, then the moves follow in algebraic notation, so databases, engines and websites can all import the same file.
Promotion is the compulsory change of a pawn that reaches the last rank into a queen, rook, bishop or knight of its own color, made as part of the same move and chosen freely, whatever has been captured so far.
The queen moves any number of squares along a rank, file or diagonal, provided the path is clear, which makes her the most powerful piece on the board.
Queenside castling is a move in which the king steps two squares toward the a-file rook and that rook jumps over to the square the king crossed, written 0-0-0 or O-O-O in notation.
A rank is any of the eight horizontal rows of the chessboard; FIDE numbers them 1 to 8 beginning on White's side, and rooks and queens slide along them while pawns climb from one rank to the next.
Resignation is a player's declaration that they give up the game, which ends it as a loss for that player unless the opponent could never checkmate, in which case the game is drawn.
The rook moves any number of squares along its rank or file, provided the path is clear, and it takes part in castling alongside the king.
The rules of chess are the Laws of Chess, the document FIDE publishes that sets out how pieces move, how a game ends, how clocks and records work, and how arbiters handle problems.
A scoresheet is the paper or electronic form on which each player writes down all the moves of the game in algebraic notation, and which both players sign or approve at the end to confirm the result.
The seventy-five-move rule ends the game in a draw automatically when each player has made at least seventy-five moves without a pawn move or a capture, unless the last move was checkmate.
A square is one of the sixty-four light or dark cells of the chessboard, each identified by a unique letter and number such as e4, and each able to hold at most one piece at a time.
The starting position is the fixed arrangement at the start of every standard game: pawns on the second and seventh ranks, pieces behind them, queens on their own color, and a light square at each player's right.
Staunton pieces are the standard design of chess set used in tournaments, with a distinct silhouette for each piece, and the design the Laws name for the specially made boards used by visually disabled players.
Threefold repetition lets the player whose turn it is claim a draw once the same position has occurred at least three times, whatever order of moves produced it.
Touch-move is the over-the-board rule that binds a player to a piece once it has been deliberately touched: your own piece has to be moved and an opponent's piece has to be captured, wherever a legal move exists.
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