parenthesis
pa-ren-the-sis
noun
A pair of round brackets ( ) used to enclose extra information in text.
"Please put the optional details in parenthesis."
noun
An explanatory word or phrase inserted into a sentence as an aside or comment.
"Her witty aside was a delightful parenthesis."
Thesaurus
Synonyms: digression, excursus, aside, divagation