Diagonal

A diagonal is a straight, slanting line of same-colored squares. Each step along it changes exactly one file and one rank at the same time. For example, c1, d2, e3, f4, g5, and h6 belong to one diagonal.

A bishop moves only on diagonals, while a queen can use them in addition to ranks and files. Neither piece can jump: a friendly piece stops the move, and an enemy piece may be captured but blocks every square beyond it.

Because every step preserves square color, a bishop remains on light squares or on dark squares for the entire game. Diagonals have different lengths depending on where they begin. The two that cross the board from corner to corner contain eight squares and are known as the long diagonals.