nLab
commutator

Definition

In rings and algebras

For $A$ a ring or associative algebra, the commutator of two elements $x,y\in A$ is the element

$$[x,y]:=xy-yx.$$[x,y] := x y - y x \,.

In groups

For $G$ a group, the group commutator of two elements $a,b\in G$ is the element

$$[a,b]:=a^{-1}{b}^{-1}ab.$$[a,b] := a^{-1} b^{-1} a b \,.

Properties

• For $A$ an associative algebra, the underlying vector space of $A$ equipped with the commutator bracket is a Lie algebra $(A,[-,-])$.