detumescence (noun) – reduction of swelling
BREAKDOWN: DE- (reversal) + TUM- (to swell) + -ESCE (action or process) + -ENCE (inclination)
This word is built on the root TUM-, which means to swell or to be proud.
Common TUM- words include tomb and tumor.
More esoteric TUM- words include contumely, tumefacient, and tumulous.