Identifier:

   *Unique;  A word, in and to itself, unique. proper nouns.

 **General; A word that can represent a "unique identifier" without the need of a "determiner" e.g. a, the, every. pronouns.

Descriptor:

    ^Unique;   A word that is used as an introduction to help define a "unique identifier" or a "general identifier". common nouns.

   ^^General;  A word that is used to define things made from matter. concrete nouns.

^^^intangible; A word is used to define things absent of matter. abstract nouns.