plural vs opera glasses

plural and opera glasses both are nouns.

Word	Noun	Adjective	Verb	Adverb
plural	Yes	Yes	No	No
opera glasses	Yes	No	No	No

plural (noun)	opera glasses (noun)
the form of a word that is used to denote more than one	(plural) an optical instrument designed for simultaneous use by both eyes

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