inessential vs incidental

inessential and incidental both are nouns.

Word	Noun	Adjective	Verb	Adverb
inessential	Yes	Yes	No	No
incidental	Yes	Yes	No	No

inessential (noun)	incidental (noun)
anything that is not essential	an item that is incidental
	(frequently plural) an expense not budgeted or not specified

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