decline vs repudiate

decline is a noun but repudiate is not a noun.

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

As verbs, repudiate is a hyponym of decline; that is, repudiate is a word with a more specific, narrower meaning than decline:

Other hyponyms of decline include disdain, freeze off, pooh-pooh, reject, scorn, spurn, turn down, contract out, regret, disobey.

decline (noun)	repudiate (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

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