Why does strain have no unit?

(N/A) Strain is defined as the ratio of the change in dimension to the original dimension of a body.
Mathematically,$\text{Strain} = \frac{\Delta L}{L}$.
Since both the numerator (change in dimension) and the denominator (original dimension) represent the same physical quantity (length),their units cancel each other out.
Therefore,strain is a dimensionless and unitless quantity.