plural form vs incidental

plural form and incidental both are nouns.

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

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

plural form (adjective)	incidental (adjective)
	(sometimes followed by `to') minor or casual or subordinate in significance or nature or occurring as a chance concomitant or consequence
	not of prime or central importance
	occurring with or following as a consequence