accidentally vs circumstantially

accidentally and circumstantially both are adverbs.

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

As adverbs, accidentally and circumstantially are synonyms defined as:

Other synonyms of accidentally include by chance, unexpectedly.

accidentally (adverb)	circumstantially (adverb)
without advance planning	insofar as the circumstances are concerned
without intention; in an unintentional manner	without advance planning
of a minor or subordinate nature	in minute detail
	according to circumstances