niche vs concavity

niche and concavity both are nouns.

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

As nouns, concavity is a hypernym of niche; that is, concavity is a word with a broader meaning than niche:

Other hypernyms of niche include concave shape, incurvation, incurvature.

niche (noun)	concavity (noun)
an enclosure that is set back or indented	the property possessed by a concave shape
a small concavity	a shape that curves or bends inward
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)