pouch vs cavity

pouch and cavity both are nouns.

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

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

Other hypernyms of pouch include enclosed space.

pouch (noun)	cavity (noun)
a small or medium size container for holding or carrying things	(anatomy) a natural hollow or sinus within the body
(anatomy) saclike structure in any of various animals (as a marsupial or gopher or pelican)	a sizeable hole (usually in the ground)
an enclosed space	soft decayed area in a tooth; progressive decay can lead to the death of a tooth
	space that is surrounded by something

pouch (verb)	cavity (verb)
swell or protrude outwards
put into a small bag
send by special mail that goes through diplomatic channels