bursa vs sac

bursa and sac both are nouns.

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

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

bursa: a small fluid-filled sac located between movable parts of the body especially at joints
sac: a structure resembling a bag in an animal

bursa (noun)	sac (noun)
a small fluid-filled sac located between movable parts of the body especially at joints	a structure resembling a bag in an animal
	a case or sheath especially a pollen sac or moss capsule
	an enclosed space