backstairs vs plural

backstairs and plural both are nouns.

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

backstairs (noun)	plural (noun)
a second staircase at the rear of a building	the form of a word that is used to denote more than one

backstairs (adjective)	plural (adjective)
secret and sly or sordid	grammatical number category referring to two or more items or units
	composed of more than one member, set, or kind