decline vs react

decline is a noun but react is not a noun.

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

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

Other hypernyms of decline include respond.

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