papilledema vs edema

papilledema and edema both are nouns.

Word	Noun	Adjective	Verb	Adverb
papilledema	Yes	No	No	No
edema	Yes	No	No	No

As nouns, edema is a hypernym of papilledema; that is, edema is a word with a broader meaning than papilledema:

papilledema: swelling of the optic disc (where the optic nerve enters the eyeball); usually associated with an increase in intraocular pressure
edema: swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities

Other hypernyms of papilledema include dropsy, hydrops, oedema.

papilledema (noun)	edema (noun)
swelling of the optic disc (where the optic nerve enters the eyeball); usually associated with an increase in intraocular pressure	swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities