circumstance vs circumstantial

circumstance is a noun but circumstantial is not a noun.

Word	Noun	Adjective	Verb	Adverb
circumstance	Yes	No	No	No
circumstantial	No	Yes	No	No

circumstance (noun)	circumstantial (noun)
information that should be kept in mind when making a decision
formal ceremony about important occasions
a condition that accompanies or influences some event or activity
the set of facts or circumstances that surround a situation or event

circumstance (adjective)	circumstantial (adjective)
	fully detailed and specific about particulars