decline vs disobey

decline is a noun but disobey is not a noun.

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

As verbs, disobey is a hyponym of decline; that is, disobey 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, repudiate.

decline (noun)	disobey (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)	disobey (verb)
grow smaller	refuse to go along with; refuse to follow; be disobedient
grow worse
show unwillingness towards
inflect for number, gender, case, etc.
go down
fall in value
not accept as true