bulla vs cyst

bulla and cyst both are nouns.

Word	Noun	Adjective	Verb	Adverb
bulla	Yes	No	No	No
cyst	Yes	No	No	No

As nouns, cyst is a hypernym of bulla; that is, cyst is a word with a broader meaning than bulla:

bulla: (pathology) an elevation of the skin filled with serous fluid
cyst: a small anatomically normal sac or bladderlike structure (especially one containing fluid)

Other hypernyms of bulla include vesicle.

bulla (noun)	cyst (noun)
the round leaden seal affixed to a papal bull	a small anatomically normal sac or bladderlike structure (especially one containing fluid)
(pathology) an elevation of the skin filled with serous fluid	a closed sac that develops abnormally in some body structure