crown jewels vs plural

crown jewels and plural both are nouns.

Word	Noun	Adjective	Verb	Adverb
crown jewels	Yes	No	No	No
plural	Yes	Yes	No	No

crown jewels (noun)	plural (noun)
regalia (jewelry and other paraphernalia) worn by a sovereign on state occasions	the form of a word that is used to denote more than one

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