oedema vs swelling

oedema and swelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
oedema	Yes	No	No	No
swelling	Yes	No	No	No

As nouns, swelling is a hypernym of oedema; that is, swelling is a word with a broader meaning than oedema:

oedema: swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities
swelling: an abnormal protuberance or localized enlargement

Other hypernyms of oedema include lump, puffiness.

oedema (noun)	swelling (noun)
swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities	the increase in volume of certain substances when they are heated (often accompanied by release of water)
	something that bulges out or is protuberant or projects from its surroundings
	an abnormal protuberance or localized enlargement