step-in vs plural

step-in and plural both are nouns.

Word	Noun	Adjective	Verb	Adverb
step-in	Yes	No	No	No
plural	Yes	Yes	No	No

step-in (noun)	plural (noun)
short underpants for women or children	the form of a word that is used to denote more than one

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