Classification of materials by conductivity:

A conductor like a metal has high conductivity and low resistance. An insulator such as glass or a vacuum cleaner with a low conductivity and high resistance has.

The conductivity of a semiconductor is the medium in general, but varies in different conditions, such as exposure of the material for electric fields or specific frequencies of light, and, most importantly, with the temperature and composition of semiconductor material.

The extent of doping in solid-state semiconductors makes a big difference in the conductivity. More doping leads to a higher conductivity. The conductivity of a solution of water is highly dependent on the concentration of dissolved salts and sometimes other chemicals, which tend to ionize in the solution.

Electrical conductivity of water is used as an indicator of how salt-free, ion-free or impurity-free sample is used, the purer the water, the lower the conductivity (the higher) of the resistance. Conductivity measurements in water are often reported as "specific conductivity", which the conductivity of the water, it was measured at 25 C.