Assuming you're talking about en passant in Chess I'll explain. Say you haven't moved a pawn and there is another pawn threatening the space one up from your pawn. Suppose you move your pawn two spaces up taking it out of harms way of your opponents pawn. En passant is when they move to the space that you would've moved to if you'd only moved the pawn up one . They take you piece and take the space you would've moved to. This move only works with pawns.
It can be used ONLY on your move, right after your opponent passes one of your advanced pawns with a pawn on its very first move. Your opponent has opted to move a pawn two squares ahead as its very first move. You have the option, on your very next move, of acting as if the pawn was only advanced one square, and you can capture the pawn (you capture it 'in passing') and advance your pawn to the square it would have occupied on a regular capture of that pawn. If you don't do it on your very next move, you lose the option. If an en passant capture is a player's only legal move, it must be done.
The 'En Passant' move was added sometime in the 15th Century .
En passant - album - was created on 1997-08-26.
En passant - 2006 is rated/received certificates of: Canada:14A
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The cast of En passant - 1984 includes: Simone Nickele Oliver Richter Stephan Samuel
The cast of Le bonheur en passant - 2003 includes: Franck Ladurelle
"by the way" is translated as "en passant" in French. The original form is "soit dit en passant" ('telling you by the way').
Chess .
it is called En Passant
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The term is 'capturing en passant.' (It's a French term.) It arises when a pawn (obviously one that has not previously moved) moves two spaces ahead, and in doing so ends up immediately beside an opponent's pawn. The opponent's pawn has the option of capturing en passant by removing the first pawn and placing his pawn in the square that the first pawn moved through. The positioning after each player has moved would be the same as if the first pawn had only moved one square forward, and then was captured in normal fashion by the opponent's pawn.