descent vs lightening

descent and lightening both are nouns.

Word	Noun	Adjective	Verb	Adverb
descent	Yes	No	No	No
lightening	Yes	No	No	No

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

descent: a movement downward
lightening: descent of the uterus into the pelvic cavity that occurs late in pregnancy; the fetus is said to have dropped

Other hyponyms of descent include drop, fall, set, cascade, shower, sinking, slide.

descent (noun)	lightening (noun)
the act of changing your location in a downward direction	changing to a lighter color
properties attributable to your ancestry	descent of the uterus into the pelvic cavity that occurs late in pregnancy; the fetus is said to have dropped
a movement downward
the hereditary derivation of an individual
a downward slope or bend
the kinship relation between an individual and the individual's progenitors