Noun

(taxonomies)

The science or the technique used to make a classification.

A classification; especially , a classification in a hierarchical system.

(taxonomy, uncountable) The science of finding, describing, classifying and naming organisms.

Noun

(en noun)

Someone who identifies; a person who establishes the identity of.

* {{quote-book, year=2001, title=The Career Guide to the Horse Industry, author=Theodore A. Landers

, passage=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). citation

* {{quote-book, year=2004, title=Great Horse Racing Mysteries: True Tales from the Track, author=John McEvoy

, passage=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 . citation

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

* {{quote-book, year=2008, author=Ted Dunstone, Neil Yager, title=Biometric System and Data Analysis

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

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).

(programming, operating systems) 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.

(databases) A primary key.