Electrical conductivity is the measure of a material's ability to allow the transport of an electric charge. Its SI is the siemens per metre, (A2s3m−3kg−1) (named after Werner von Siemens) or, more simply, Sm−1
Electrical conductance is an electrical phenomenon where a material contains movable particles with electric charge (such as electrons), which can carry electricity. When a difference of electrical potential is placed across a conductor, its electrons flow, and an electric current appears.
A conductor such as a metal has high conductivity, and an [[Insulator (electricity)|insulator[[ like glass or a vaccum has low conductivity. A semiconductor has a conductivity that varies widely under different conditions .