coincidence vs accident

coincidence and accident both are nouns.

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

As nouns, accident is a hypernym of coincidence; that is, accident is a word with a broader meaning than coincidence:

coincidence: an event that might have been arranged although it was really accidental
accident: anything that happens suddenly or by chance without an apparent cause

Other hypernyms of coincidence include chance event, fortuity, stroke.

coincidence (noun)	accident (noun)
the temporal property of two things happening at the same time	anything that happens suddenly or by chance without an apparent cause
the quality of occupying the same position or area in space	an unfortunate mishap; especially one causing damage or injury
an event that might have been arranged although it was really accidental