En passant
Last updated on Wed, 03/12/2008 at 6:00pm.
En passant (from French: "in [the pawn's] passing") is a maneuver in chess when a player moves a pawn two squares forward from its starting position, and an opposing pawn could have captured it if it had only moved one square forward. The En passant rule was introduced in 1490.
In this situation, the opposing pawn may, on the immediately subsequent move, capture the pawn as if it had only moved one square forward; the resulting position would then be the same as if the pawn had only moved one square forward and the opposing pawn had captured normally. En passant must be done on the very next turn, or the right to do so is lost. This move can be written as "e.p."
Here is an example:
In the second diagram, White can NOT capture en passant: