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.

Noun

(en noun)

A non-existent or empty value or set of values.

Zero]] quantity of [[expression, expressions; nothing.

(Francis Bacon)

Something that has no force or meaning.

(computing) the ASCII or Unicode character (), represented by a zero value, that indicates no character and is sometimes used as a string terminator.

(computing) the attribute of an entity that has no valid value.

Since no date of birth was entered for the patient, his age is null .

One of the beads in nulled work.

(statistics) null hypothesis