# constant

A constant is a mathematical quantity that is not variable. Constants occur in almost
all polynomials, in the form of either coefficients or addends.
Thus in *ax*^{3} + *bx*^{2} + *cx* + *d*, each of *a*, *b*, *c*, *d* is
a constant; should the expression be set to zero then the values of the
constants determine the values of *x* for which the equation holes;
should the expression be a function then
the constants determine the values of *x* for which *f*(*x*)
is defined. Constant addends are usually symbolized by *c*, *C*, *k*, or *K*, though this is by no means universal.

Some constants are naturally occurring. One such as pi,
which is of considerable importance in mensuration; another is *e*.
Physical quantities whose scalar is constant,
such as *c*, the speed of light,
or *G*, the gravitational
constant, are termed physical constants.