- the electrode or terminal by which current leaves an electrolytic cell, voltaic cell, battery, etc.
- the positive terminal of a voltaic cell or battery.
- the negative terminal, electrode, or element of an electron tube or electrolytic cell.
- the negative electrode in an electrolytic cell; the electrode by which electrons enter a device from an external circuit
- the negatively charged electron source in an electronic valve
- the positive terminal of a primary cell
1834, from Latinized form of Greek kathodos “a way down,” from kata- “down” (see cata-) + hodos “way” (see cede). Proposed by the Rev. William Whewell (1794-1866), English polymath, and published by English chemist and physicist Michael Faraday (1791-1867). So called from the path the electric current was supposed to take. Related: Cathodic; cathodal. Cathode ray first attested 1880, but the phenomenon known from 1859; cathode ray tube is from 1905.
- The negative electrode in an electrolytic cell, toward which positively charged particles are attracted. The cathode has a negative charge because it is connected to the negatively charged end of an external power supply.
- The source of electrons in an electrical device, such as a vacuum tube or diode.
- The positive electrode of a voltaic cell, such as a battery. The cathode gets its positive charge from the chemical reaction that happens inside the battery, not from an external source. Compare anode.