Identity element
WordNet
noun
(1) An operator that leaves unchanged the element on which it operates
"The identity under numerical multiplication is 1"
WiktionaryText
Noun
- A member of a structure which, when applied to any other element via a binary operation induces an identity mapping; more specifically, given an 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 if both are true