HQ vs plural

HQ and plural both are nouns.

Word	Noun	Adjective	Verb	Adverb
HQ	Yes	No	No	No
plural	Yes	Yes	No	No

HQ (noun)	plural (noun)
the military installation from which a commander performs the functions of command	the form of a word that is used to denote more than one

HQ (adjective)	plural (adjective)
	grammatical number category referring to two or more items or units
	composed of more than one member, set, or kind