Definition of cathode in US English:



  • 1The negatively charged electrode by which electrons enter an electrical device.

    The opposite of anode
    • ‘Oxygen enters at the cathode, where it combines with electrons and is split into ions that travel through the electrolyte to react with fuel at the anode.’
    • ‘An electron originating near the planar cathode and ultimately collected at electrode A will induce an equal charge at A and B during most of its journey.’
    • ‘The fact that identical electrons were emitted from cathodes of a range of materials under a range of conditions strongly suggested that the electron is a fundamental constituent of all atoms.’
    • ‘Those same ions would then flow to the cathode, and after electrons were added, would end up as pure copper.’
    • ‘The opening focuses the electrons emitted from the cathode onto the anode to a spot size preferably less than 40 nanometers.’
    1. 1.1 The positively charged electrode of an electrical device, such as a primary cell, that supplies current.
      • ‘But because electrons must be supplied to the cathode by an external power source to drive this process, the cathode in an electrolytic cell has a negative charge.’
      • ‘The trouble with the fuel cell is that it requires a barrier between the anode and the cathode because the oxidizing and reducing agents will corrode catalytic elements if allowed to intermix.’
      • ‘Most fuel cells use a polymer electrolyte membrane to separate the cathode and anode.’
      • ‘The electrons on the anode migrate via a wire to the cathode, the other electrode in the fuel cell, where they are electrochemically assisted to combine with the protons and produce hydrogen gas.’
      • ‘Therefore, in electrolytic cells, the cathode is the negative terminal and the anode is the positive terminal.’


Mid 19th century: from Greek kathodos ‘way down’, from kata- ‘down’ + hodos ‘way’.