parenthesis

(pə-rĕnˈthĭ-sĭs)

1. Either or both of the upright curved lines, ( ), used to mark off explanatory or qualifying remarks in writing or printing or enclose a sum, product, or other expression considered or treated as a collective entity in a mathematical operation.
2. a. A qualifying or amplifying word, phrase, or sentence inserted within written matter in such a way as to be independent of the surrounding grammatical structure.
   b. A comment departing from the theme of discourse; a digression.
3. An interruption of continuity; an interval: “This is one of the things I wasn't prepared for—the amount of unfilled time, the long parentheses of nothing” (Margaret Atwood).