Origin square

Every move has a starting point. The origin square is the square the moving piece leaves. It is identified by board coordinates, which combine a letter for the file with a number for the rank.

The origin tells us which piece moved, helps verify whether its route was possible, and distinguishes between identical pieces that could reach the same destination. In algebraic notation, the system that records moves with letters and numbers, the origin is usually implied but may be added partly or fully to remove ambiguity.

In a capture, the origin is still the square occupied by the capturing piece before it moved. In castling, a special move involving the king and a rook, technical systems may record each piece's origin and destination separately even though the rules count it as one king move.