\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.
2. Anything added; increase; augmentation; as, a piazza is an
   addition to a building.
3. (Math.) That part of arithmetic which treats of adding
   numbers.
4. (Mus.) A dot at the right side of a note as an indication
   that its sound is to be lengthened one half. [R.]
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.
6. (Her.) Something added to a coat of arms, as a mark of
   honor; -- opposed to {abatement}.
{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.
Syn: Increase; accession; augmentation; appendage; adjunct.