Absolute Value

The Absolute Value of a number answers the question: how far away from 0 is it? It ignores the sign, so it's always zero or positive.

It's written with vertical bars, $|x|$. For example, $|-3| = 3$ and $|3| = 3$.

Formally:

$|x| = \begin{cases} x & \text{if } x \geq 0 \\ -x & \text{if } x < 0 \end{cases}$