lymphedema vs edema

lymphedema and edema both are nouns.

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

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

lymphedema: swelling (usually in the legs) caused by lymph accumulating in the tissues in the affected areas
edema: swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities

Other hypernyms of lymphedema include dropsy, hydrops, oedema.

lymphedema (noun)	edema (noun)
swelling (usually in the legs) caused by lymph accumulating in the tissues in the affected areas	swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities