accidentally vs accidental

accidentally is not a noun while accidental is a noun.

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

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

accidentally (adjective)	accidental (adjective)
	not of prime or central importance
	happening by chance or unexpectedly or unintentionally

accidentally (adverb)	accidental (adverb)
without advance planning
without intention; in an unintentional manner
of a minor or subordinate nature