Constant \Con"stant\, n.
   1. That which is not subject to
         change; that which is
      invariable.
      [1913
         Webster]

   2. (Math.) A quantity that does not change
         its value; -- used
      in countradistinction to variable.
      [1913
         Webster]

   3. (Astron.) A number whose value, when
         ascertained (as by
      observation) and substituted in a
         general mathematical
      formula expressing an
         astronomical law, completely
      determines that law and
         enables predictions to be made of
      its effect in
         particular cases.
      [Webster 1913 Suppl.]

   4.
         (Physics) A number expressing some property or condition
  
            of a substance or of an instrument of precision; as,
         the
      dielectric constant of quartz; the collimation
         constant of
      a transit instrument.
      [Webster
         1913 Suppl.]

   5. (Computers) a data structure that does
         not change during
      the course of execution of a
         program. It may be a number,
      a string, or a more
         complex data structure; -- contrasted
      with variable.
      [PJC]


           Aberration
         constant, or Constant of aberration
         (Astron.),
      a number which by substitution in the
         general formula for
      aberration enables a prediction
         to be made of the effect
      of aberration on a star
         anywhere situated. Its value is
      20[sec].47.

  
         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.

   Gravitation
         constant
         (Physics), the acceleration per unit
      of time produced
         by the attraction of a unit of mass at
      unit distance.
         When this is known the acceleration
      produced at any
         distance can be calculated.

   Solar constant
         (Astron.), the quantity of heat received by
      the earth
         from the sun in a unit of time. It is, on the C.
      G.
         S. system, 0.0417 small calories per square centimeter
    
          per second. --Young. [Webster 1913 Suppl.]

   {Constant
         of integration} (Math.), an undetermined constant
     
         added to every result of integration.
      [1913 Webster +
         Webster 1913 Suppl.]