Editing Identifier (section)

{{Short description|Name that identifies a specific entity}}
[[File:4373 Russian license plate Toyota car.jpg|thumb|400x400px|alt=A Russian license plate with the value "C051KO199" is mounted on the front grille of a Toyota car|[[Vehicle registration plate|Registration plates]] are used to display identifiers for [[Motor vehicle|motor vehicles]].]]

An '''identifier''' is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of objects, where the "object" or class may be an idea, person, physical [[countable]] object (or class thereof), or physical [[mass noun|noncountable]] substance (or class thereof). The abbreviation '''ID''' often refers to identity, identification (the process of identifying), or an identifier (that is, an instance of identification). An identifier may be a word, number, letter, symbol, or any combination of those.

The words, numbers, letters, or symbols may follow an [[code|encoding system]] (wherein letters, digits, words, or symbols ''stand for'' [represent] ideas or longer names) or they may simply be arbitrary. When an identifier follows an encoding system, it is often referred to as a '''code''' or '''id&nbsp;code'''.  For instance the [[ISO/IEC 11179]] metadata registry standard defines a code as ''system of valid symbols that substitute for longer values'' in contrast to identifiers without symbolic meaning. Identifiers that do not follow any encoding scheme are often said to be '''arbitrary&nbsp;Ids'''; they are arbitrarily assigned and have no greater meaning. (Sometimes identifiers are called "codes" even when they are actually arbitrary, whether because the speaker believes that they have deeper meaning or simply because they are speaking casually and imprecisely.)

The [[unique identifier]] ('''UID''') is an identifier that refers to ''only one instance''—only one particular object in the universe. A [[part number]] is an identifier, but it is not a ''unique'' identifier—for that, a [[serial number]] is needed, to identify ''each instance'' of the part design. Thus the ''identifier'' "Model&nbsp;T" identifies the ''class'' ''(model)'' of automobiles that Ford's [[Ford Model T|Model&nbsp;T]] comprises; whereas the ''unique identifier'' "Model&nbsp;T&nbsp;Serial Number&nbsp;159,862" identifies one specific member of that class—that is, one particular Model&nbsp;T car, owned by one specific person.

The concepts of ''name'' and ''identifier'' are [[denotation|denotatively]] equal, and the terms are thus denotatively [[synonym]]ous; but they are not always [[connotation|connotatively]] synonymous, because '''[[code name]]s''' and '''Id numbers''' are often connotatively distinguished from names in the sense of traditional [[natural language]] naming. For example, both "[[Jamie Zawinski]]" and "[[Netscape]] employee number 20" are identifiers for the same specific human being; but normal English-language connotation may consider "Jamie Zawinski" a "name" and not an "identifier", whereas it considers "Netscape&nbsp;employee&nbsp;number&nbsp;20" an "identifier" but not a "name." This is an [[emic]] indistinction rather than an [[etic]] one.