\Pa*ren"the*sis\, n.; pl. {Parentheses}. [NL., fr.
Gr. ?, fr. ? to put in beside, insert; ? beside + ? in + ? to
put, place. See {Para-}, {En-}, 2, and {Thesis}.]
1. A word, phrase, or sentence, by way of comment or
   explanation, inserted in, or attached to, a sentence which
   would be grammatically complete without it. It is usually
   inclosed within curved lines (see def. 2 below), or
   dashes. ``Seldom mentioned without a derogatory
   parenthesis.'' --Sir T. Browne.
         Don't suffer every occasional thought to carry you
         away into a long parenthesis.         --Watts.
2. (Print.) One of the curved lines () which inclose a
   parenthetic word or phrase.
Note: Parenthesis, in technical grammar, is that part of a
      sentence which is inclosed within the recognized sign;
      but many phrases and sentences which are punctuated by
      commas are logically parenthetical. In def. 1, the
      phrase ``by way of comment or explanation'' is inserted
      for explanation, and the sentence would be
      grammatically complete without it. The present tendency
      is to avoid using the distinctive marks, except when
      confusion would arise from a less conspicuous
      separation.