Definition:Complex Modulus

Definition
Let $z = a + i b$ be a complex number.

Then the (complex) modulus of $z$ is written $\left\vert{z}\right\vert$ and is defined as:


 * $\left\vert{z}\right\vert := \sqrt {a^2 + b^2}$

Real Number
Note that when $y = 0$, i.e. when $z$ is wholly real, this becomes $\left\vert{z}\right\vert = \sqrt{x^2} = \left\vert{x}\right\vert$, which is consistent with the definition of the absolute value of $x$.

Also see

 * Modulus of Complex-Valued Function