- (algebra) An element of a structure which, when applied to any other element via a binary operation, induces an identity mapping.
Specifically, for binary operation *, an element i is:
- a left identity if i * x = x for any x in the structure,
- a right identity, x * i = x for any x in the structure,
- simply an identity element or (for emphasis) a two-sided identity if both are true.
member of a structure