Exchange (chess) 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,
Fairy chess piece opponent's pieces). With multiple royal pieces the game can be won by capturing one of them (absolute royalty), or capturing all of them (extinction royalty). The rules can also impose a limit to the number of royals that are allowed to be left in check. In Spartan chess black has two kings, and they both cannot be left in check even though they both cannot be captured in one turn. The following table shows some game pieces of unorthodox chess, from fairy chess problems and chess variants (including historical and regional ones), and the six orthodox chess pieces. The columns