In electricity, the capability of a body, a system or an Electric circuit for storing electric charge. Capacitance, in units of farads, is expressed as the ratio of stored charge in coulombs to the applied potential difference in volts.

In electric circuits, devices designed to store charge are called capacitors. When alternating current flows through a capacitor, the capacitor produces a reactance, inversely proportional to the capacitance, that resists the current flow (Impedance).