plural vs main office

plural and main office both are nouns.

Word	Noun	Adjective	Verb	Adverb
plural	Yes	Yes	No	No
main office	Yes	No	No	No

plural (noun)	main office (noun)
the form of a word that is used to denote more than one	(usually plural) the office that serves as the administrative center of an enterprise

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