sac vs bodily cavity

sac and bodily cavity both are nouns.

Word	Noun	Adjective	Verb	Adverb
sac	Yes	No	No	No
bodily cavity	Yes	No	No	No

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

Other hypernyms of sac include cavity, cavum.

sac (noun)	bodily cavity (noun)
a structure resembling a bag in an animal	(anatomy) a natural hollow or sinus within the body
a case or sheath especially a pollen sac or moss capsule
an enclosed space