An Etymological Dictionary of Astronomy and Astrophysics

A mathematical operation that combines two numbers, quantities, sets, etc., to give a third. For example, multiplication of two numbers is a binary operation.

A binary operation * on a set S is → commutative if a * b = b * a for all a, b∈ S.

A binary operation * on a set S is → associative if (a * b) * c = a * (b * c) for all a, b, c∈ S.

See also: → binary; → operation.