The *absolute value* of a real number \(x\) is denoted by \(|x|\) and is defined as \[ |x| = \begin{cases} x &\text{if $x \geq 0$}\\
-x & \text{if $x < 0$.} \end{cases}\]

Therefore, the absolute value is always greater than or equal to zero, and describes how far away the corresponding number is from the origin.

The absolute value of a real number is sometimes referred to as its modulus.