declivity vs incline

declivity and incline both are nouns.

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

As nouns, incline is a hypernym of declivity; that is, incline is a word with a broader meaning than declivity:

Other hypernyms of declivity include side, slope.

declivity (noun)	incline (noun)
a downward slope or bend	an inclined surface connecting two levels
	an elevated geological formation

declivity (verb)	incline (verb)
	make receptive or willing towards an action or attitude or belief
	feel favorably disposed or willing
	be at an angle
	lower or bend (the head or upper body), as in a nod or bow
	bend or turn (one's ear) towards a speaker in order to listen well
	have a tendency or disposition to do or be something; be inclined