swelling vs tumidity

swelling and tumidity both are nouns.

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

As nouns, tumidity is a hyponym of swelling; that is, tumidity is a word with a more specific, narrower meaning than swelling:

swelling (noun)	tumidity (noun)
the increase in volume of certain substances when they are heated (often accompanied by release of water)	slight swelling of an organ or part
something that bulges out or is protuberant or projects from its surroundings
an abnormal protuberance or localized enlargement