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, physical [countable] object (or class thereof), or physical [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.