If the membrane potential is anything other than 0 mV, it is said to be polarized. The magnitude of membrane polarization is proportional to the concentration of ionic charges that are separated. By convention, the ECF is said to have a charge of 0 mV. A negative sign (-) is used to denote an excess of negative charge in the ICF, and a positive sign (+) is used to denote an excess of positive charge in the ICF