: the electrode of an electrochemical cell at which reduction occurs: as a: the negative terminal of an electrolytic cell b: the positive terminal of a storage battery that is delivering current
: the electron-emitting electrode of an electron tube—compare anode
Terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. In a battery or other source of direct current, the cathode is the positive terminal. In a passive load it is the negative terminal. In an electron tube, such as a cathode-ray tube, electrons stream off the cathode and travel through the tube toward the anode.