noun pl. parentheses -·ses′ (-sēz′)

1. an additional word, clause, etc. placed as an explanation or comment within an already complete sentence: in writing or printing it is usually marked off by curved lines, dashes, or commas
2. either or both of the curved lines, (), used to mark off parenthetical words, etc. or to enclose mathematical or logical symbols that are to be treated as a single term
3. an episode or incident, often an irrelevant one; interlude

Etymology: LL < Gr < parentithenai, to put beside < para-, beside (see para-) + entithenai, to insert < en-, in + tithenai, to put, place: see do