Identifier

n. one who identifies; one who associates himself with a particular cause or idea

Identifiers (IDs) are lexical tokens that name entities. The concept is analogous to that of a "name". Identifiers are used extensively in virtually all information processing systems. Naming entities makes it possible to refer to them, which is essential for any kind of symbolic processing.
See more at Wikipedia.org...

Noun
1. a symbol that establishes the identity of the one bearing it
(hypernym) symbol

v. identify, zero in

1. In telecommunications and data processing systems, one or more characters used to identify, name, or characterize the nature, properties, or contents of a set of data elements. 2. A string of bits or characters that names an entity, such as a program, device, or system, in order that other entities can call that entity. 3. In programming languages, a lexical unit that names a language object, such as a variable, array, record, label, or procedure. Note: An identifier is placed in a label. The label is attached to, is a part of, or remains associated with, the information it identifies. If the label becomes disassociated from the information it identifies, the information may not be accessible.