vesica vs sac

vesica and sac both are nouns.

Word	Noun	Adjective	Verb	Adverb
vesica	Yes	No	No	No
sac	Yes	No	No	No

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

vesica (noun)	sac (noun)
a distensible membranous sac (usually containing liquid or gas)	a structure resembling a bag in an animal
	a case or sheath especially a pollen sac or moss capsule
	an enclosed space