field glasses vs plural

field glasses and plural both are nouns.

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

field 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

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