Cathode

A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead–acid battery. This definition can be recalled by using the mnemonic CCD for cathode current departs. Conventional current describes the direction in which positive charges move. Electrons, which are the carriers of current in most electrical systems, have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow: this means that electrons flow into the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode. The electrode through which conventional current flows the other way, into the device, is termed an anode.