The Collaborative International Dictionary of English v.0.48:

Addition \Ad*di"tion\, n. [F. addition, L. additio, fr. addere
   to add.]
   1. The act of adding two or more things together; -- opposed
      to subtraction or diminution. "This endless addition
      or addibility of numbers." --Locke.
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   2. Anything added; increase; augmentation; as, a piazza is an
      addition to a building.
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   3. (Math.) That part of arithmetic which treats of adding
      numbers.
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   4. (Mus.) A dot at the right side of a note as an indication
      that its sound is to be lengthened one half. [R.]
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   5. (Law) A title annexed to a man's name, to identify him
      more precisely; as, John Doe, Esq.; Richard Roe, Gent.;
      Robert Dale, Mason; Thomas Way, of New York; a mark of
      distinction; a title.
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   6. (Her.) Something added to a coat of arms, as a mark of
      honor; -- opposed to abatement.
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   Vector addition (Geom.), that kind of addition of two
      lines, or vectors, AB and BC, by which their sum is
      regarded as the line, or vector, AC.
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   Syn: Increase; accession; augmentation; appendage; adjunct.
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