ETYM French identité, Late Lat. identitas, from Latin idem the same, from the root of is he, that; cf. Skr. idam this. Related to Item.
The distinct and recognizable nature of an individual, which results from a unique combination of characteristics and qualities. In philosophy, identity is the sameness of a person, which may continue in spite of changes in bodily appearance, personality, intellectual abilities, memory, and so on. In psychology, identity refers to one's conception of oneself and sense of continuous being, particularly as an individual distinguishable from, but interacting, with others.
1. The distinct personality of an individual regarded as a persisting entity; SYN. individuality.
2. Exact sameness; SYN. identicalness, indistinguishability.
3. Collective aspect of the set of characteristics by which a thing is recognizable or known.
4. An operator that leaves unchanged the element on which it operates; SYN. identity element, identity operator.

In mathematics, a number or operation that leaves others unchanged when combined with them. Zero is the identity for addition; one is the identity for multiplication. For example, 7 + 0 = 7 7 x 1 = 7