Conductivity is a noun: it is how well a material lets electricity or heat pass through. It is not simply “can it or can’t it” — scientists measure it, and some metals score higher than others. Silver has extremely high electrical conductivity; copper is close behind, which is why houses are wired with copper. Rubber has very low conductivity, so it is used to stop current. There is electrical conductivity and thermal conductivity (heat), and they are not the same number. Because the word names a quality, say the conductivity of copper is high, not copper is conductivity.