react vs decline

react is not a noun while decline is a noun.

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

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

react (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

react (verb)	decline (verb)
undergo a chemical reaction; react with another substance under certain conditions	grow smaller
show a response or a reaction to something	grow worse
act against or in opposition to	show unwillingness towards
	inflect for number, gender, case, etc.
	go down
	fall in value
	not accept as true