opera glasses vs plural

opera glasses and plural both are nouns.

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

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

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