niche vs concave shape

niche and concave shape both are nouns.

Word	Noun	Adjective	Verb	Adverb
niche	Yes	No	No	No
concave shape	Yes	No	No	No

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

Other hypernyms of niche include concavity, incurvation, incurvature.

niche (noun)	concave shape (noun)
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)