Definition:Relative Error/Also defined as

Definition
Let $x$ be an approximation to a (true) value $X$.

The relative error in $x$ can also be defined as:


 * $\dfrac {\size {X - x} } x$

where $\size {X - x}$ denotes the absolute value of $X - x$.

This can be particularly useful when the true value $X$ is only speculated.