- Noun. Someone who identifies; a person who establishes the identity of.
- Noun. Something that identifies or uniquely points to something or someone else.
- Noun. A guidebook that helps determine the specific class of an object (such as a mushroom, herb, fish, bird, drug, or mineral), or its individual identity (such as that of a star).
- Noun. (programming, operating system) A formal name used in source code to refer to a variable, function, procedure, package, etc. or in an operating system to refer to a process, user, group, etc.
- Noun. (databases) A primary key.