identity
Pluralidentities
- 1The character or sense of self that sets a person or group apart from others and lets them be recognized over time.
Adolescence is often when a person's identity begins to take shape.
The festival celebrates the cultural identity of the region's indigenous communities.
UsageCommon phrases: a sense of identity, a strong identity, and cultural or national identity.
Similarselfhood, individuality, personality
Note
Sounds and systems have identities as well as people and nations. Fausto Cercignani wrote in 2021 of a Middle English vowel that preserved its identity into the early Modern English period, meaning it stayed distinct from its neighbors. Individuality stresses being unlike others, while identity also covers being recognizable as the same self over time.
- 2Which particular person or thing someone or something is, as shown by details such as a name that prove it.
Officials will not release the victim's identity until her family has been notified.
Thieves used his stolen identity to open several credit card accounts.
UsageOften with verbs like reveal, confirm, conceal or protect, and in proof of identity and identity theft.
Note
The identity on a police report or a bank form: a matter of record, established by facts such as a name rather than by how anyone feels. That sets it apart from the sense of selfhood, where identity is something a person has or explores.
- 3A name or persona (a mask or public face) that one presents to the world and is known by.
The author wrote under a secret identity for years before revealing her real name.
Witnesses are sometimes given a new identity to keep them safe.
UsageOften a secret, false or new identity; people write or live under an identity.
- 4An element of an algebraic structure that leaves any element unchanged when combined with it under the structure's operation.
In any group, the identity combines with each member to give back that same member.
The number one serves as the multiplicative identity in ordinary arithmetic.
Note
An identity is always relative to an operation, though mathematicians often say simply the identity when the operation is clear. Zero is the identity for addition and one is the identity for multiplication, which gives the common phrases additive identity and multiplicative identity. A set with two operations can therefore have two different identities, as the real numbers do. The operation must be named or understood from context.
Less common meanings
- 5The quality or fact of two or more things being the same; sameness.
Members of the two unions felt a strong identity of interests, since both groups faced the same cuts to pay and benefits.
Philosophers debate the identity of an object that gradually replaces all its parts.
UsageUsually identity of or identity between: an identity of interests, the identity between two genes.
Similarsameness, uniformity, identicalness
Oppositedifference, dissimilarity, distinctness
Note
Here the word claims that two things are the same, whether in their qualities or as one and the same thing. A 1997 chapter on hydrothermal vent fauna in Advances in Marine Biology writes of the identity of two species that seemed to be different stages of the same species. Sameness sits oddly beside the "selfhood" meaning, which is about what sets one thing apart.
- 6An equation that holds true for every possible value of its variables.
The Pythagorean identity relates the sine and cosine of any angle.
Proving the equation is an identity means showing it holds for all inputs.
- 7A function that maps every element of its domain to itself, returning each input unchanged.
Composing any function with the identity leaves that function unchanged.
The identity maps each point of the plane onto itself.
Note
The function that does nothing is written f(x) = x and is usually called the identity function or identity map. It matters because of composition: following or preceding any function with it changes nothing. That makes it the neutral element for the operation of composing functions. In computing, the same idea describes a routine that hands its input back unaltered.
Checked 6 Nov 2026 · 4 facts
- The identity function returns each input unchanged and is expressed by f(x) = x. mat112.uncg.edu
- Composing a function with the identity on its domain or codomain leaves the function unchanged. cs.montana.edu
- The identity map acts as a neutral element under composition. math.stonybrook.edu
- Computing has identity functions that return their input unchanged. downloads.haskell.org
- 8A famous or well-known person, especially one many people can recognize.
The retired coach remained a beloved identity in the community for decades.
Several sporting identities attended the charity dinner.
UsageOften in a local identity, an old identity or a well-known identity.
Similarcelebrity, personality
Note
Australian and New Zealand English use the word for a person everyone in a place knows. Its favorite company is old, as in an old identity or a well-known old identity. The Age of Melbourne used exactly that phrase in 1887 for James Conroy, a man drowned at Williamstown. Readers from elsewhere may mistake it for the "persona" meaning.
Practice
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Origin
From Middle French "identité", which came from Latin "identitas".
Checked 6 Nov 2026 · 2 facts
- English identity derives from Middle French identité. en.wiktionary.org
- French identité derives from Latin identitas. en.wiktionary.org