concavity vs impression

concavity and impression both are nouns.

Word	Noun	Adjective	Verb	Adverb
concavity	Yes	No	No	No
impression	Yes	No	No	No

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

concavity (noun)	impression (noun)
the property possessed by a concave shape	an impressionistic portrayal of a person
a shape that curves or bends inward	the act of pressing one thing on or into the surface of another
	(dentistry) an imprint of the teeth and gums in wax or plaster
	an outward appearance
	a vague idea in which some confidence is placed
	a clear and telling mental image
	a symbol that is the result of printing or engraving
	all the copies of a work printed at one time
	a concavity in a surface produced by pressing