plural vs backstairs

plural and backstairs both are nouns.

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

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

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