real number

The quantity of real numbers is usually called absolute value or modulus. It is written as | x | and is defined as follows:

| x | = x, if x ≥ 0 | x | = -x, if x

This gives the distance from zero on a straight line. For example, the modulus of -5 is |-5|=5.

[edit] plural number

Similarly, a complex quantity is called a module, which gives the distance from zero on the Argentine map. This formula giving the modulus of complex numbers is the same as Pythagorean theorem:

For example, the modulus of -3+4i is 5.