descent vs declivity

descent and declivity both are nouns.

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

As nouns, descent and declivity are synonyms defined as:

Other synonyms of descent include declension, declination, decline, downslope, fall.

descent (noun)	declivity (noun)
the act of changing your location in a downward direction	a downward slope or bend
properties attributable to your ancestry
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