| 50 move rule |
A rule in chess, which states that a player can claim a draw after 50 moves whilst in the meantime no pawn has been moved and no piece has been taken. |
| Alpha-beta pruning |
Significant improvement of the Minimax algorithm, in which parts of the search tree can be “cut off” without coming to a different resulting move. |
| Castling |
A special move in chess where both the players’s king and one the rooks are moved. For castling, different conditions must be met. |
| Chess 960 |
A chess variant developed by Bobby Fischer. The initial position is drawn from 960 possibilities. Also known as Fischer Random Chess. |
| to drop (a piece) |
A beginner’s mistake in chess. A piece is dropped, if it is moved to a field attacked by the opponent and can be taken by him or her without risk or disadvantage. |
| Draw |
A chess game which ends with no winner. There are various ways to end it with a draw, one of them is stalemate. |
| Half-move |
Single action (move) of an individual player, unlike the sequence of a white and a black move which is counted as a move e.g. when numbering. |
| En passant |
A special pawn move in chess. If a pawn moves on two squares and an opposing pawn could capture him, if he would advance only one square, the latter pawn may capture it en passant. |
| Endgame |
The final stage of a chess game. It is characterised when only a few types of pieces are left on the board. |
| Engine |
Part of a chess program which calculates the moves. Typically, an engine has no graphical user interface. Also known as ‘chess engine’. |
| FEN |
Forsyth-Edwards Notation. Compact representation of a chess board position as a character string. Supported by many chess tools. Used in DokChess by unit and integration tests. Explanation see e.g. [Wikipedia] (https://en.wikipedia.org/wiki/Forsyth–Edwards_Notation) |
| FIDE |
Fédération Internationale des Échecs, international chess organisation |
| Fork |
A tactic in chess in which a piece attacks two (or more) of the opponent’s pieces simultaneously. |
| Knight fork |
Particularly common form of a fork with a knight as attacking piece. |
| Mate |
End of a chess game in which the king of the player to move is attacked and the player has no valid move left (i.e. can not escape the attack). The player has lost. Also known as ‘checkmate’. |
| Minimax algorithm |
Algorithm to determine the best move under the consideration of all options of both players. |
| Opening |
First stage of a chess game. Knowledge and best practices of the first moves in chess fill many books and large databases. |
| Polyglot Opening Book |
Binary file format for opening libraries. Unlike many other formats for this purpose the documentation of it is freely accessible. |
| Promotion |
A rule in chess which states that a pawn who reached the opponent’s base line is immediately converted into a queen, rook, bishop or knight. |
| Skewer |
A tactic in chess in which a straight line passing piece stands on a rank, file or diagonal with two opponents pieces and forces the fore of the two pieces to move away. |
| Stalemate |
End of a chess game in which the player to move does not have a valid move, but his or her king is not under attack. The game is considered a draw. |
| Threefold repetition |
A rule in chess, which states that a player can claim a draw if the same position occurs at least three times. |
| WinBoard protocol |
See XBoard protocol. |
| XBoard protocol |
Text-based protocol for communication between chess frontends and engines. Also referred to as “WinBoard” or (more rarely) as “Chess Engine Communication Protocol”. |