modifier

Short definition from Wiktionary

Noun

1. 1
   One who, or that which, modifies.
2. 2
   A word, phrase, or clause that limits or qualifies the sense of another word or phrase. (It may be any of the following: an adjective phrase, an adverb phrase, a prepositional phrase, a noun phrase, or a subordinate clause.)
3. 3
   A keyword that qualifies the meaning of other code.
4. 4
   Ellipsis of modifier key.