In mathematics, the value, or magnitude, of a
number irrespective of its sign (denoted
|n|), and defined as the positive square root
of n^2. It is often referred to as the
modulus of n, written mod n. For example, 5
and -5 have the same absolute value:
|5| = |-5| = 5. For a complex number, the
absolute value is its distance to the origin
when it is plotted on an Argand diagram, and
can be calculated (without plotting) by
applying the Pythagorean theorem. By
definition, the absolute value of any complex
number a + bi is given by the expression |a +
bi| = `sqrt'(a^2 + b^2).

Subject by: Russell Webb