repudiate vs decline

repudiate is not a noun while decline is a noun.

Word	Noun	Adjective	Verb	Adverb
repudiate	No	No	Yes	No
decline	Yes	No	Yes	No

As verbs, decline is a hypernym of repudiate; that is, decline is a word with a broader meaning than repudiate:

Other hypernyms of repudiate include refuse.

repudiate (noun)	decline (noun)
	a downward slope or bend
	a gradual decrease; as of stored charge or current
	change toward something smaller or lower
	a condition inferior to an earlier condition; a gradual falling off from a better state; decline

repudiate (verb)	decline (verb)
refuse to acknowledge, ratify, or recognize as valid	grow smaller
cast off	grow worse
reject as untrue, unfounded, or unjust	show unwillingness towards
refuse to recognize or pay	inflect for number, gender, case, etc.
	go down
	fall in value
	not accept as true