plural vs incidental expense

plural and incidental expense both are nouns.

Word	Noun	Adjective	Verb	Adverb
plural	Yes	Yes	No	No
incidental expense	Yes	No	No	No

plural (noun)	incidental expense (noun)
the form of a word that is used to denote more than one	(frequently plural) an expense not budgeted or not specified

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