Board and rules

A chessboard is a grid of 64 alternating squares arranged in eight ranks and eight files.

One of the chessboard's 64 spaces, uniquely identified by a letter and a number.

A vertical set of eight chessboard squares identified by one letter from a through h.

A horizontal set of eight chessboard squares identified by one number from 1 through 8.

A slanting line of same-colored squares that changes one file and one rank at each step.

The central area of the board, with d4, d5, e4, and e5 forming its core.

One of the two eight-square diagonals that cross the entire board from one corner to the opposite corner.

A movable chess unit; in the official rules, the word also includes pawns.

The piece that cannot be left under attack; if it is attacked and no permitted reply exists, the game ends.

A long-range piece that moves along ranks, files, and diagonals without jumping over other pieces.

A long-range piece that moves any number of squares along ranks or files.

A long-range piece that moves diagonally and always remains on squares of one color.

A piece that jumps to a square two steps in one direction and one step perpendicular to it.

A piece that advances toward the opponent, captures diagonally, and can transform on the farthest rank.

The collective name for bishops and knights.

The collective name for rooks and queens.

A bishop that moves only among the board's thirty-two light squares.

A bishop that moves only among the board's thirty-two dark squares.

The official arrangement of all thirty-two pieces before the first move.

The rank closest to a player, where that side's king, queen, rooks, bishops, and knights begin.

The horizontal row numbered 1, located along White's side of the board.

The horizontal row numbered 7, where Black's pawns begin and a white pawn stands one rank from promotion.

A square on the farthest rank that a pawn reaches and must use to become another piece.

The side with the light-colored pieces, which makes the first move of the game.

The side with the dark-colored pieces, which replies after White's opening move.

One of the 32 squares that form the lighter half of the board's alternating pattern.

One of the 32 squares that form the darker half of the board's alternating pattern.

The half of the board formed by the e-, f-, g-, and h-files, where the kings begin.

The half of the board formed by the a-, b-, c-, and d-files, where the queens begin.

The board and 32 pieces used to play, although some rules use “chess set” for the pieces alone.

The game state at a particular moment, including pieces, side to move, and relevant special rights.

A board designed so that the position and pieces can be identified and handled mainly through touch.

A square that shares an edge or a corner with another square on the board.

A situation in which one side has only its king left, with no pawns or other pieces.

A pawn on a bishop file, meaning the c-file or the f-file.

The correct placement of the board, with a light square at each player's near right corner.

A large board that reproduces a position so a group can see it easily.

A physical board that detects pieces and moves so they can be recorded, stored, or transmitted to other systems.

An outer board region formed by the a-, b-, and c-files or by the f-, g-, and h-files.

A pawn on the e-file, called the king's file because the king starts there.

A pawn on a knight file, meaning the b-file or the g-file.

A queen, rook, bishop, or knight that replaces a pawn when it reaches the last rank.

The rank farthest from a pawn's starting side, where that pawn must become another piece.

A pawn on the d-file, called the queen's file because the queen starts there.

A pawn on a rook file, meaning the a-file or h-file at the edge of the board.

A bishop, rook, or queen that can travel any number of squares along an allowed clear line.

The square a piece occupies at the beginning of a game with the standard setup.

A recognizable chess-piece design used as the practical standard for modern competitive play.

A move that follows every applicable rule and does not leave the player's own king in check.

A move that breaks a rule, especially one that leaves or places the player's own king in check.

An in-person rule requiring a deliberately touched piece to be moved or captured when a legal option exists.

A phrase spoken before touching a piece to show that it will only be adjusted within its square.

A position in which the king is attacked and must be made safe on the immediate move.

A check with no legal defense, ending the game immediately in victory for the attacking player.

A drawn position where the player to move is not in check but has no legal move.

A move that removes an opposing piece by occupying its square, except for the special en passant capture.

A capture answering an opponent's capture, usually by immediately taking the piece that just captured.

A special move in which the king moves two squares toward a rook and that rook crosses to the king's other side.

Castling toward the kingside rook, leaving the king on g1 or g8 and the rook on f1 or f8.

Castling toward the queenside rook, leaving the king on c1 or c8 and the rook on d1 or d8.

A special pawn capture that immediately takes a pawn just advanced two squares as though it had advanced one.

Promotion replaces a pawn that reaches the last row with a queen, rook, bishop, or knight of the same color.

Underpromotion means promoting a pawn to a rook, bishop, or knight instead of choosing a queen.

Interposition stops a rook, bishop, or queen check by placing another piece between the attacker and the king.

A discovered check occurs when one piece moves away and uncovers another piece's attack on the king.

Double check occurs when one move leaves the king attacked by two pieces at the same time.

Perpetual check is a forced sequence of repeated attacks on the king that can return to the same cycle again and again.

A draw offer proposes ending the game without a winner and has that effect only if the opponent accepts.

Resignation is a voluntary declaration that a player will not continue, normally ending the game in an immediate loss.

Flag-fall is the signal that a player's allotted time on the chess clock has expired.

Timeout means a player failed to complete the required moves before their chess clock reached zero.

A forfeit is a game loss imposed for absence, a rule violation, or failure to meet a competition condition.

Threefold repetition allows a draw claim when the same position appears for the third time with the same legal possibilities.

The game is automatically drawn when the same position appears at least five times, with no claim required.

A player may claim a draw after 50 moves by each side without a pawn move or a capture.

The game is automatically drawn after 75 moves by each player without a pawn move or capture, unless the last move checkmates.

A position in which neither player can deliver checkmate through any possible sequence of legal moves.

A common term for pieces that cannot produce checkmate, judged by legal mating possibility rather than material value alone.

A legal action taken by one player on their turn to change the position on the board.

A device with two connected time displays that separately measures each player's available thinking time.

A piece attacks a square or opposing piece when it could capture there according to its movement pattern.

A square controlled by an opposing piece because that piece could capture there under its movement rules.

A position state showing whether a player still retains the legal right to castle with each rook.

A legal move that removes the immediate attack on the player’s own king.

The indicator on each side of a chess clock showing that a player’s allotted time has expired.

A move that has reached its final rules state, usually after the board move is made and the clock is pressed.

An electronic two-display clock that controls playing time and supports programmable modes such as increment and delay.

A piece accidentally moved away from its correct place without necessarily constituting a chess move.

A pawn’s optional first move of two squares, legal only when both squares ahead are empty.

A temporary chance to capture an enemy pawn immediately after its initial two-square advance.

A board state that could not have been reached through any sequence of legal moves.

The rules consequence applied when a player completes a move that does not meet the legal requirements.

The exact move formally declared before play to support certain draw claims under the rules.

A competition situation that departs from the correct state or procedure and requires a rules response.

A move that permanently changes a piece, right, or historically significant part of the position state.

A move whose physical execution has become fixed under the rules, before any separate completion by the clock.

The pieces and position circumstances that allow some checkmate to be reached through legal moves.

A non-electronic chess clock with two linked mechanisms and a physical flag indicating the end of a time period.

A clock device that records how many times each player has pressed their clock control.

The requirement to execute each move with one hand and press the clock with that same hand.

The square occupied by a piece immediately before it begins a move.

The procedure for reconstructing an earlier position and resuming the game from it after an irregularity.

To operate the button or lever that stops your time and starts your opponent's time.

A candidate move that follows basic piece movement but may still be illegal because it leaves the moving side's king in check.

Promotion in which a pawn reaching the farthest row is replaced by a new queen of the same color.

An irregularity in which the players begin with the opposite colors from those assigned to them.

In technical analysis, a non-pawn move to an empty square that does not reset the fifty-move count.

A rules-based identity between positions with the same pieces, side to move, and possible moves.

An illegal result created by moving so that the moving side's king remains or becomes attacked.

The player, White or Black, who has the right and obligation to make the next move.

An accessible chessclock that speaks the time and, depending on the model, the move count.

The square occupied by the moving piece when a move has been made.

Either of the two parts of a chessclock that shows one player's remaining time.

The physical execution of one move with both hands, contrary to the competitive one-hand requirement.

A final result in which one player wins the game and the other receives a loss.

A final result in which one player loses the game and the opponent receives the win.

A final result in which the game ends without either player winning.

The game ends as a draw when one player offers that result and the other accepts.

A result awarded because the opponent loses under tournament rules rather than through the normal outcome of a played game.

A loss imposed by a competition rule or arbiter's ruling even when the board position was not lost.

A win awarded without starting the game because the assigned opponent does not appear or cannot play.

A player's absence from a round in which an opponent had been assigned, especially when the player misses the permitted arrival deadline.

The maximum permitted delay after a round starts before a player normally loses for failing to appear.

A draw that arises when a rules condition is met without either player having to claim it.

A rules-based request by which a player invokes a right that the arbiter must verify.

A draw that ends the game only after a correct claim by the player having the move.

An exceptional result in which both players receive a loss because of an infringement or administrative ruling.

A formal request for the arbiter to declare a draw because a rule-based condition has been met.

A draw when a player's time expires but the opponent cannot checkmate through any legal sequence of moves.

The scoring unit awarded to a player for the result of one game.

The formal record of how a game ended for each player.

An optional US Chess procedure for claiming a draw in certain time scrambles with very little practical chance of losing.

A situation in which both clocks show expired time and the order of the two flag-falls cannot be established.

A specialized ICCF request to set the result of an ending exactly resolved by a database covering up to seven pieces.

A game that started but whose final result is not yet known or available.

A scheduled or recorded pairing in which the two players did not contest valid moves against each other.