# Commutativity

A property of algebraic operations (cf. Algebraic operation). For addition and multiplication, commutativity is expressed by the formulas $$a+b=b+a,\quad \text{ and } \quad ab=ba.$$ A binary operation $*$ is commutative (or, what is the same, satisfies the law of commutativity) if in the given algebraic system the identity $a*b=b*a$ holds.