What is called as relative error? Define fractional error.

(N/A) Relative error is defined as the ratio of the mean absolute error to the mean value of the quantity measured.
Mathematically,it is expressed as: $\text{Relative Error} = \frac{\Delta a_{\text{mean}}}{a_{\text{mean}}}$.
Fractional error is another term used for relative error. It represents the uncertainty in a measurement relative to the size of the measurement itself. When the relative error is expressed in percentage,it is called percentage error,given by: $\text{Percentage Error} = \frac{\Delta a_{\text{mean}}}{a_{\text{mean}}} \times 100\%$.