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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. ==General discussion== 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. A ''forced exchange'' is an exchange in a position where one of the players is required to initiate or undergo an exchange, either because no alternative play is allowed by chess rules or because the consequence of not making the exchange would be unacceptably detrimental to that player's game. Many exchanges can be offered, but they are not forced. In such cases, the player presented with the possibility of an exchange may decide to make the initial capture, may decline making the initial capture, or may even move to avoid the exchange. The player can weigh the advantages and disadvantages of each move to decide. For a prospective uneven exchange, the values of the pieces are often the deciding factor. Chess positions are often set up where a player's piece on a certain square is defended by one or more of his other pieces. This typically means that if an opponent's piece captures the defended piece, the capturing piece would be subject to recapture by a defending piece (''defender''). An opponent's piece in a position to capture a given piece could be considered an attacking piece (''attacker''). Positions could develop where a player's piece on a square has one or more attackers and one or more defenders. This is a common way in which exchanges could occur, although there are other ways also. In such positions, a player with the attacking piece(s) may decide whether it is worthwhile for him to initiate a capture likely to result in recapture, likely decided by the value of the pieces to be taken in the ensuing exchange. Pinned pieces often cannot be counted on being attackers or defenders. In chess, a sacrifice is the deliberate giving up of a piece by a player, allowing or forcing an opponent to capture the piece or exchange it for a lower value piece. In a desperado situation, a trapped piece which would inevitably be lost can sometimes be exchanged for another piece, even if it has lower value, in order to minimize net material loss for the player having the inevitably lost piece. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Exchange (chess)」の詳細全文を読む スポンサード リンク
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