underpants vs plural

underpants and plural both are nouns.

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

underpants (noun)	plural (noun)
an undergarment that covers the body from the waist no further than to the thighs; usually worn next to the skin	the form of a word that is used to denote more than one

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