identity

plural identities

1. countableuncountableSameness, identicalness; the quality or fact of (several specified things) being the same.

   Benjamin Franklin established the identity of electricity and lightning.

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   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 each Chapter the ſame; how fully aſſured muſt we needs be of theſe Identities, the Agreements of theſe two Paralleliſms (thoſe paſſages onely excepted of which I have given ſo fair an account) perfectly exhauſting the whole ſubſtance of each Chapter?

   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, page 264

   […] suggesting the two are different stages of the same species. The identity of the two species is further suggested by allozyme analysis […]

   1997, “Hydrothermal Vent Fauna”, in Advances in Marine Biology: The Biogeography of the Oceans, page 111

   Synonyms: identicalness, identicality, sameness, identicality, identicalness, sameliness, sameness, uniformity · Antonyms: unidenticality, nonidentity, difference, differentiation, differentness, distinction, distinguishedness, nonidentity

2. countableuncountableThe 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.

   This nation has a strong identity.

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   I've been through so many changes, I have no sense of identity.

   His own identity was fading out into a grey impalpable world: the solid world itself which these dead had one time reared and lived in was dissolving and dwindling.

   1904–1907 (date written), James Joyce, “The Dead”, in Dubliners, London: Grant Richards, published June 1914, →OCLC, page 277

   On the other hand, ME /ɛu/ preserved its identity into the early Modern English period, and the early writers on orthography and pronunciation normally distinguish between lME /iu/ and lME /ɛu/, the latter of which occurs in words with eME /ɛː/ like dew (OE dēaw), few (OE fēawe), hew (OE hēawan), sew (eME ē < ĕ, OE seowian), shrew (OE scrēawa), etc.

   2021 July 28, Fausto Cercignani, “On the alleged existence of a vowel /yː/ in early Modern English”, in English Language and Linguistics, volume 26, number 2, Cambridge University Press, →DOI, page 2

   Synonyms: individuality, beinghood, individuality, ipseity, personality, personhood, personness, selfdom

3. countableuncountableA name or persona—a mask or appearance one presents to the world—by which one is known.

   This criminal has taken on several identities.

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   In this show, the competitor's identity will remain secret until after the vote.

4. countableuncountablemathematicsAn 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. countableuncountablealgebraAny function which maps all elements of its domain to themselves.

   Synonyms: identity function

6. countableuncountablealgebraAn 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. AustraliaNew ZealandcountableuncountableA 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

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   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