Exchange (chess)

In the tactics and strategy in the board game of chess, an exchange (exchanging) or trade (trading) of chess pieces is series of closely related moves, typically sequential, in which the two players capture each other's pieces. Any types of pieces except the kings may possibly be exchanged, i.e. captured in an exchange, although a king can capture an opponent's piece. Either the player of the white or the black pieces may make the first capture of the other player's piece in an exchange, followed by the other player capturing a piece of the first player, often referred to as a recapture. Commonly, the word "exchange" is used when the pieces exchanged are of the same type or of about equal value, which is an even exchange. According to chess tactics, a bishop and a knight are usually of about equal value. If the values of the pieces exchanged are not equal, then the player who captures the higher value of piece(s) can be said to be up the exchange or wins the exchange, while the opponent who captures the lower value of piece(s) is down the exchange or loses the exchange. Exchanges occur very frequently in chess, in almost every game and usually multiple times per game. Exchanges are often related to the tactics or strategy in a chess game, but often simply occur over the course of a game.

The exchange of a rook for bishop or knight is an uneven exchange because a rook is generally more valuable than a bishop or knight. A minor exchange is a less commonly used term which refers to the capture of the opponent's bishop for the player's knight.

A player's objective in a chess game is to checkmate the opponent's king and/or to avoid checkmate of his own king. In this ultimate sense, the value of chess pieces remaining in a game does not matter. Although no official score is kept of the value of pieces on the board for each player, much experience in chess play has determined approximate average strategic and tactical value of various pieces relative to a pawn, which is given a value = 1. Bishops and knights have about the same value at 3, rooks are valued at about 5, and a queen is valued at about 9. Since the king is indispensable, it has infinite value. Pieces, especially as distinguished by their value, are often referred to collectively as material in chess. These values are not absolute because the usefulness of a piece also depends on its position in a particular game, commonly in a way hard to quantify. For example, an advanced passed pawn with a good probability of promotion is commonly more valuable in a particular situation than a backward or isolated pawn that is not a passed pawn.

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