D defs.my
Entry 6 senses Webster, 1913

Addition

/əd-ĭsh'-ən/ · Ad·di·tion · IPA /əˈdɪʃ.ən/
01 n. The act of adding two or more things together; -- opposed to subtraction or diminution.
  1. 1.
    The act of adding two or more things together; -- opposed to subtraction or diminution.
  2. 2.
    Anything added; increase; augmentation; as, a piazza is an addition to a building.
  3. 3.
    That part of arithmetic which treats of adding numbers.(Math.)
  4. 4.
    A dot at the right side of a note as an indication that its sound is to be lengthened one half.(Mus.) [R.]
  5. 5.
    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.(Law)
  6. 6.
    Something added to a coat of arms, as a mark of honor; -- opposed to abatement.(Her.)
Phrases & compounds
Vector addition — that kind of addition of two lines, or vectors, AB and BC, by which their sum is regarded as the line, or vector, AC.