Castling in the context of "Rook (chess)"

The king (♔, ♚) is one of the six types of pieces in the game of chess and represents the most important unit on the board. It may move to any adjacent square that is not controlled by an enemy piece; it may also perform, in tandem with the rook, a special move called castling. If a player's king is threatened with capture, it is said to be in check, and the player must remove or evade the threat of capture immediately, such as by moving it away from the attacked square. If this cannot be done, the king is said to be in checkmate, resulting in a loss for that player. A player cannot make any move that places their own king in check. Despite this, the king can become a strong offensive piece in the endgame or, rarely, the middlegame.

In algebraic notation, the king is abbreviated by the letter K among English speakers. The white king starts the game on e1; the black king starts on e8. Unlike all other pieces, each player can have only one king, and the kings are never removed from the board during the game.

Indian chess is the name given to regional variations of chess played in India in the 18th and 19th centuries. It is distinct from chaturanga. There are several such variations, all quite similar to modern rules, with variants regarding castling, pawn promotion, etc.