impinging vs collision

impinging and collision both are nouns.

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

As nouns, collision is a hyponym of impinging; that is, collision is a word with a more specific, narrower meaning than impinging:

impinging: the physical coming together of two or more things
collision: (physics) a brief event in which two or more bodies come together

Other hyponyms of impinging include hit, engagement, interlocking, mesh, meshing, flick, impact, touch, touching.

impinging (noun)	collision (noun)
the physical coming together of two or more things	a conflict of opposed ideas or attitudes or goals
	an accident resulting from violent impact of a moving object
	(physics) a brief event in which two or more bodies come together