1. One of a number of identical markings, usually inlaid into the surface above the rail cushions, used as target or reference points. Three equally spaced diamonds are normally between each pocket on a pool table. On a carom table, the pockets themselves are replaced by additional diamonds. Diamonds get their name from the shape of the markings traditionally used; though many today are round , square, etc., these rail markings are still referred to as "diamonds". They are also referred to as sights, especially in British English . (See also diamond system .)

2. A particular shape of ball rack , in the form of a parallelogram ("diamond shape "), used for racking games of nine-ball and seven-ball , though the triangle rack can also be used for the former, and hexagonal racks also exist for the latter. (See also triangle .)