aside vs parenthesis

aside and parenthesis both are nouns.

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

As nouns, aside and parenthesis are synonyms defined as:

Other synonyms of aside include digression, divagation, excursus.

aside (noun)	parenthesis (noun)
a line spoken by an actor to the audience but not intended for others on the stage	either of two punctuation marks (or) used to enclose textual material
a message that departs from the main subject	a message that departs from the main subject

aside (adverb)	parenthesis (adverb)
on or to one side
out of the way (especially away from one's thoughts)
in reserve; not for immediate use
not taken into account or excluded from consideration
placed or kept separate and distinct as for a purpose
in a different direction