commutative semigroup
A semigroup is commutative
if the defining binary operation
is commutative (http://planetmath.org/Commutative). That is, for all , the identity
holds.
Although the term Abelian semigroup is sometimes used, it is more common simply to refer to such semigroups as commutative semigroups.
A monoid which is also a commutative semigroup is called a commutative monoid.