concavity vs niche

concavity and niche both are nouns.

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

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

concavity (noun)	niche (noun)
the property possessed by a concave shape	an enclosure that is set back or indented
a shape that curves or bends inward	a small concavity
	a position particularly well suited to the person who or organization which occupies it
	(ecology) the status of an organism within its environment and community (affecting its survival as a species)