< 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.
- The set of behavioral or personal characteristics by which an individual is recognizable as a member of a group.
- The distinct personality of an individual regarded as a persisting entity; individuality.
- The element of a set of numbers that when combined with another number under a particular binary operation leaves the second number unchanged. For example, 0 is the identity element under addition for the real numbers, since for any real number a, a + 0 = a, and 1 is the identity element under multiplication for the real numbers, since a X 1 = a.