approval vs message

approval and message both are nouns.

Word	Noun	Adjective	Verb	Adverb
approval	Yes	No	No	No
message	Yes	No	Yes	No

As nouns, message is a hypernym of approval; that is, message is a word with a broader meaning than approval:

Other hypernyms of approval include content, subject matter, substance.

approval (noun)	message (noun)
the formal act of approving	content communicating a message; what something is about
a message expressing a favorable opinion	a communication (usually brief) that is written or spoken or signaled
a feeling of liking something or someone good
acceptance as satisfactory