brain edema vs dropsy

brain edema and dropsy both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain edema	Yes	No	No	No
dropsy	Yes	No	No	No

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

brain edema: swelling of the brain due to the uptake of water in the neuropile and white matter
dropsy: swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities

Other hypernyms of brain edema include edema, hydrops, oedema.

brain edema (noun)	dropsy (noun)
swelling of the brain due to the uptake of water in the neuropile and white matter	swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities