fossa vs concave shape

fossa and concave shape both are nouns.

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

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

Other hypernyms of fossa include bodily cavity, cavity, cavum, concavity, incurvation, incurvature.

fossa (noun)	concave shape (noun)
largest carnivore of Madagascar; intermediate in some respects between cats and civets	a shape that curves or bends inward
a concavity in a surface (especially an anatomical depression)