long johns vs plural

long johns and plural both are nouns.

Word	Noun	Adjective	Verb	Adverb
long johns	Yes	No	No	No
plural	Yes	Yes	No	No

long johns (noun)	plural (noun)
warm underwear with long legs	the form of a word that is used to denote more than one

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