\Sub*trac"tion\, n. [L. subtractio a drawing back.
See {Subtract}, and cf. {Substraction}.]
1. The act or operation of subtracting or taking away a part.
2. (Math.) The taking of a lesser number or quantity from a
   greater of the same kind or denomination; an operation for
   finding the difference between two numbers or quantities.
3. (Law) The withdrawing or withholding from a person of some
   right to which he is entitled by law.
Note: Thus the subtraction of conjugal rights is when either
      the husband or wife withdraws from the other and lives
      separate without sufficient reason. The subtraction of
      a legacy is the withholding or detailing of it from the
      legatee by the executor. In like manner, the
      withholding of any service, rent, duty, or custom, is a
      subtraction, for which the law gives a remedy.
      --Blackstone.