Noun

(en noun)

A pointer or index that indicates something.

A meter or gauge.

The needle or dial on such a meter.

(chemistry) Any of many substances, such as litmus, used to indicate the concentration of a substance, or the degree of a reaction.

(ecology) A plant or animal whose presence is indicative of some specific environment.

(economics) A measure, such as unemployment rate, which can be used to predict economic trends.

(UK, Australia) A trafficator.

A bird, the honeyguide.

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.