standards of 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.

   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.

   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.
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.

See all 7 meanings of identity