\Con"stant\, a. [L. onstans, -antis, p. pr. of constare
to stand firm, to be consistent; con- + stare to stand: cf.
F. constant. See {Stand} and cf. {Cost}, v. t.]
1. Firm; solid; fixed; immovable; -- opposed to fluid. [Obs.]
         If . . . you mix them, you may turn these two fluid
         liquors into a constant body.         --Boyle.
2. Not liable, or given, to change; permanent; regular;
   continuous; continually recurring; steadfast; faithful;
   not fickle.
         Both loving one fair maid, they yet remained
         constant friends.                     --Sir P.
                                               Sidney.
         I am constant to my purposes.         --Shak.
         His gifts, his constant ourtship, nothing gained.
                                               --Dryden.
         Onward the constant current sweeps.   --Longfellow.
3. (Math. & Physics) Remaining unchanged or invariable, as a
   quantity, force, law, etc.
4. Consistent; logical. [Obs.] --Shak.
Syn: Fixed; steadfast; unchanging; permanent; unalterable;
     immutable; invariable; perpetual; continual; resolute;
     firm; unshaken; determined.
Usage: {Constant}, {Continual}, {Perpetual}. These words are
       sometimes used in an absolute and sometimes in a
       qualified sense. Constant denotes, in its absolute
       sense, unchangeably fixed; as, a constant mind or
       purpose. In its qualified sense, it marks something as
       a ``standing'' fact or occurence; as, liable to
       constant interruptions; constantly called for.
       Continual, in its absolute sense, coincides with
       continuous. See {Continuous}. In its qualified sense,
       it describes a thing as occuring in steady and rapid
       succession; as, a round of continual calls;
       continually changing. Perpetual denotes, in its
       absolute sense, what literally never ceases or comes
       to an end; as, perpetual motion. In its qualified
       sense, it is used hyperbolically, and denotes that
       which rarely ceases; as, perpetual disturbance;
       perpetual noise; perpetual intermeddling.

\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.

\Con"stant\, n.
1. (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.
2. (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.
{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.
{Constant of integration} (Math.), an undetermined constant
   added to every result of integration.
{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.