identifier

noun

1. Someone who identifies; a person who establishes the identity of someone or something.

   “The Identifier personally inspects each horse in each race by verifying the lip tattoo, body color, head and leg markings, scars, and chestnut (night eyes).”

   “The foal papers are documents recording the horse's registration; no horse can start in any race unless his papers are in the hands of the track's identifier.”

   “Here, we would use the anonymous key technique to obtain a quantum identification protocol AKI of the challenge-response type in which the identifier cannot pretend to be the identifiee […]”

2. Something that identifies or uniquely points to something or someone else.

   “Prehistoric artists used hand-prints in cave paintings, perhaps as a 'signature'. They might be considered the earliest example of a biometric identifier.”

   “The source stated that the alleged victims wanted the paperwork released after the settlement, but with names and identifiers removed.”

3. One who identifies as a particular type or role; one who says and believes that they are a certain thing.

   “While the DOJ and BOJS already calculate data by gender, trans identifiers are not included, it is solely by men and women”

4. 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).
5. 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.
6. A code that distinguishes a particular element from all other elements in a document.
7. A primary key.