unessential vs accidental

unessential is not a noun while accidental is a noun.

Word	Noun	Adjective	Verb	Adverb
unessential	No	Yes	No	No
accidental	Yes	Yes	No	No

unessential (noun)	accidental (noun)
	a musical notation that makes a note sharp or flat or natural although that is not part of the key signature

unessential (adjective)	accidental (adjective)
not basic or fundamental	not of prime or central importance
	happening by chance or unexpectedly or unintentionally