undies vs plural

undies and plural both are nouns.

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

undies (noun)	plural (noun)
women's underwear	the form of a word that is used to denote more than one

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