knee breeches vs plural form

knee breeches and plural form both are nouns.

Word	Noun	Adjective	Verb	Adverb
knee breeches	Yes	No	No	No
plural form	Yes	No	No	No

knee breeches (noun)	plural form (noun)
(used in the plural) trousers ending above the knee	the form of a word that is used to denote more than one