Definition:Sign of Number

Definition
The sign of a number is the symbol indicating whether it is:
 * positive, denoted by the symbol $+$

or:
 * negative, denoted by the symbol $-$.

Hence a number's sign has evolved to define the fact of the number being positive or negative independently of the symbol itself.

Thus:
 * the sign of $3.14159$ is positive

and
 * the sign of $-75$ is negative.

Also see

 * Definition:Signum Function