fossa vs cavity

fossa and cavity both are nouns.

Word	Noun	Adjective	Verb	Adverb
fossa	Yes	No	No	No
cavity	Yes	No	No	No

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

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

fossa (noun)	cavity (noun)
largest carnivore of Madagascar; intermediate in some respects between cats and civets	(anatomy) a natural hollow or sinus within the body
a concavity in a surface (especially an anatomical depression)	a sizeable hole (usually in the ground)
	soft decayed area in a tooth; progressive decay can lead to the death of a tooth
	space that is surrounded by something