excursus vs message

excursus and message both are nouns.

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

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

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

excursus (noun)	message (noun)
a message that departs from the main subject	content communicating a message; what something is about
	a communication (usually brief) that is written or spoken or signaled