In
mathematics, a
binary operation is
commutative if changing the order of the
operands does not change the result. It is a fundamental property of many
binary operations, and many
mathematical proofs depend on it. Most familiar as the name of the property that says or , the property can also be used in more advanced settings. The name is needed because there are operations, such as
division and
subtraction, that do not have it (for example, ), such operations are
not commutative, or
noncommutative operations. The idea that simple operations, such as
multiplication and
addition of numbers, are commutative was for many years implicitly assumed and the property was not named until the 19th century when mathematics started to become formalized.