Resistance of a conductor is given by R = $\rho {l \over A}$, where $\rho$ is the specific resistance, $l$ is the length and A is the cross-sectional area of the conductor. Now, when $l$ = 1 and A = 1, R = $\rho$.

So specific resistance or resistivity of a material may be defined as the resistance of a specimen of the material having unit length and unit cross-section. Hence, specific resistance is a property of a material and it will increase with the increase of temperature, but will not vary with the dimensions (length, crosssection) of the conductor.