Source : Webster's Revised Unabridged Dictionary (1913)

Constant \Con"stant\, n.
   1. That which is not subject to change; that which is
      invariable.

   2. (Math.) A quantity that does not change its value; -- used
      in countradistinction to {variable}.

   {Absolute constant} (Math.), one whose value is absolutely
      the same under all circumstances, as the number 10, or any
      numeral.

   {Arbitrary constant}, an undetermined constant in a
      differential equation having the same value during all
      changes in the values of the variables.