The reciprocal of the resistivity of a material is called its:

Explanation

Conductivity measures how readily a material carries current and is the reciprocal of resistivity, with units of siemens per metre. Admittance is the reciprocal of impedance and reactance is the opposition offered by a capacitor or inductor, both of which belong to circuit analysis rather than to material properties. Copper has a high conductivity and rubber a very low one.