Temperature coefficient of resistance (${\alpha }_R=R^{-1}dR/dT$)

The fractional change in electrical resistance per unit temperature change, with geometry and other conditions specified. For a small interval around $T_0$, $R(T)\simeq R(T_0)[1+{\alpha }_R(T-T_0)]$. Low $|{\alpha }_R|$ is useful in stable resistors.