The electrostatic system of units is a system of units used to measure electrical quantities of electric charge, current, and voltage, within the centimeter gram second (or "CGS") metric system of units. In electrostatic units, electrical charge is defined via the force it exerts on other charges. The various units of the e.s.u. system have specific names obtained by prefixing more familiar names with $stat$, but are often referred to purely descriptively as the 'e.s. unit of capacitance', etc.