excursus vs digression

excursus and digression both are nouns.

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

As nouns, excursus and digression are synonyms defined as:

Other synonyms of excursus include aside, divagation, parenthesis.

excursus (noun)	digression (noun)
a message that departs from the main subject	a turning aside (of your course or attention or concern)
	wandering from the main path of a journey
	a message that departs from the main subject