Pronunciation: (ī-den'ti-tē, i-den'-),[key] —n., —pl.-ties. 1. the state or fact of remaining the same one or ones, as under varying aspects or conditions: The identity of the fingerprints on the gun with those on file provided evidence that he was the killer. 2. the condition of being oneself or itself, and not another: He doubted his own identity. 3. condition or character as to who a person or what a thing is: a case of mistaken identity. 4. the state or fact of being the same one as described.
5. the sense of self, providing sameness and continuity in personality over time and sometimes disturbed in mental illnesses, as schizophrenia.
6. exact likeness in nature or qualities: an identity of interests. 7. an instance or point of sameness or likeness: to mistake resemblances for identities. 8. Logic.an assertion that two terms refer to the same thing.
9. Math. a. an equation that is valid for all values of its variables.
b. Also called identity element, unit element, unity. an element in a set such that the element operating on any other element of the set leaves the second element unchanged.
c. the property of a function or map such that each element is mapped into itself.
d. the function or map itself.
10. Australian Informal.an interesting, famous, or eccentric resident, usually of long standing in a community.