identity

Noun

identity (countable and uncountable, plural identities)

1. Sameness, identicalness; the quality or fact of (several specified things) being the same.
   • Benjamin Franklin established the identity of electricity and lightning.
   • But whenas a leſſer number of Agreements in each Paralleliſm (provided there were nothing contrary) could not but have been a ſtrong preſumption of the Identity of the Subjects of the Viſions in each Chapter, I mean, That the Two-horned Beaſt and the Whore are one, and the Seven-headed Beaſt in...1664, H[enry] More, chapter X, in Synopsis Prophetica; or, The Second Part of the Modest Enquiry into the Mystery of Iniquity: […], London: […] James Flesher, for William Morden […], →OCLC, book I...

   Synonyms:

   identicalness, identicality, sameness, sameliness, uniformity

   Antonyms:

   unidenticality, nonidentity, difference, differentiation, differentness, distinction, distinguishedness, diversity

2. The difference or character that marks off an individual or collective from the rest of the same kind; selfhood; the sense of who something or someone or oneself is, or the recurring characteristics that enable the recognition of such an individual or group by others or themselves.
   • I've been through so many changes, I have no sense of identity.
   • This nation has a strong identity.

   Synonyms:

   individuality, beinghood, ipseity, personality, personhood, personness, selfdom, selfhood, selfness, selfship

3. A name or persona—a mask or appearance one presents to the world—by which one is known.
   • This criminal has taken on several identities.
   • In this show, the competitor's identity will remain secret until after the vote.
4. An equation which always holds true regardless of the choice of input variables.
   • The equation (x+y)(x−y) = x²−y² is an algebraic identity. It is true regardless of the values of x and y.
5. Any function which maps all elements of its domain to themselves.

   Synonyms:

   identity function

6. An element of an algebraic structure which, when applied to another element under an operation in that structure, yields this second element.
   • Zero is the identity for the addition of real numbers.
7. (Australia, New Zealand) A well-known or famous person.
   • The body of a well known old identity named James Conroy […] was found in the water yesterday afternoon…1887 July 19, “Drowned at Williamstown”, in The Age, Melbourne
   • The 79-year-old man who died days after he was struck by a car in Westport was a local identity who was well known for his walks around town.2026 June 15, Chris Marriner, “‘The Coast was his home’: Local identity dies days after he was hit by a car”, in Stuff

   Synonyms:

   celebrity, personality