noun, plural i·den·ti·ties.
- an equation that is valid for all values of its variables.
- Also called identity element, unit element, unity. an element in a set such that the element operating on any other element of the set leaves the second element unchanged.
- the property of a function or map such that each element is mapped into itself.
- the function or map itself.
- identification parade,
- identification tag,
- identity card,
- identity crisis,
- identity disorder,
- identity element,
- identity function
Origin of identity
noun plural -ties
- that relation that holds only between any entity and itself
- an assertion that that relation holds, as Cicero is Tully
- an equation that is valid for all values of its variables, as in (x – y)(x + y) = x ² – y ². Often denoted by the symbol ≡
- Also called: identity element a member of a set that when operating on another member, x, produces that member x: the identity for multiplication of numbers is 1 since x .1 = 1. x = xSee also inverse (def. 2b)
Word Origin for identity
c.1600, "sameness, oneness," from Middle French identité (14c.), from Late Latin (5c.) identitatem (nominative identitas) "sameness," from ident-, comb. form of Latin idem (neuter) "the same" (see identical); abstracted from identidem "over and over," from phrase idem et idem. [For discussion of Latin formation, see entry in OED.] Earlier form of the word in English was idemptitie (1560s), from Medieval Latin idemptitas. Term identity crisis first recorded 1954. Identity theft attested from 1995.