collision vs accident

collision and accident both are nouns.

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

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

collision (noun)	accident (noun)
a conflict of opposed ideas or attitudes or goals	anything that happens suddenly or by chance without an apparent cause
an accident resulting from violent impact of a moving object	an unfortunate mishap; especially one causing damage or injury
(physics) a brief event in which two or more bodies come together