digression vs parenthesis

digression and parenthesis both are nouns.

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

As nouns, digression and parenthesis are synonyms defined as:

digression and parenthesis: a message that departs from the main subject

Other synonyms of digression include aside, divagation, excursus.

digression (noun)	parenthesis (noun)
a turning aside (of your course or attention or concern)	either of two punctuation marks (or) used to enclose textual material
wandering from the main path of a journey	a message that departs from the main subject
a message that departs from the main subject