happenstance vs coincidence

happenstance and coincidence both are nouns.

Word	Noun	Adjective	Verb	Adverb
happenstance	Yes	No	No	No
coincidence	Yes	No	No	No

As nouns, happenstance and coincidence are synonyms defined as:

happenstance and coincidence: an event that might have been arranged although it was really accidental

happenstance (noun)	coincidence (noun)
an event that might have been arranged although it was really accidental	the temporal property of two things happening at the same time
	the quality of occupying the same position or area in space
	an event that might have been arranged although it was really accidental