What does cathode mean?
A cathode is one of the two electrodes found in devices through which electric current passes — the other being the anode. In an electrolytic cell or an electron tube such as an old-fashioned television's cathode ray tube, the cathode is the negative electrode, releasing electrons into the circuit or serving as the site of chemical reduction. In a battery that is discharging, by contrast, the cathode becomes the positive terminal, a reversal that often surprises students. Coined in the 1830s from Greek roots meaning 'downward way', the word entered English during the pioneering era of electrochemistry, when scientists like Faraday were first mapping how electricity moves through matter. Today 'cathode' remains standard vocabulary in chemistry, physics, and electronics, appearing in contexts ranging from lithium-ion battery design to vacuum tubes and X-ray equipment. Though technical rather than everyday, it is a precise and useful term for anyone describing how electrical devices work.
nounThe negatively charged electrode in an electrical device such as a vacuum tube, electrolytic cell, or battery, at which reduction occurs or from which electrons flow. In a discharging battery the cathode is the positive terminal.
- The negative electrode in an electrolytic cell or electron tube, from which current exits the device or at which reduction takes place.
- The positive terminal of a primary cell or battery that is delivering current.
"Electrons stream off the hot cathode and race toward the anode inside the vacuum tube."
"In the electrolysis of water, hydrogen gas bubbles up around the cathode."
"Older televisions produced their picture using a cathode ray tube that fired electrons at a phosphor screen."
Regular plural, formed by adding -s.
"Both cells use zinc cathodes coated with a thin layer of copper."
Coined by William Whewell in 1834 at Michael Faraday's request, 'cathode' literally means 'way down' in Greek — a name invented over tea for a phenomenon nobody yet understood.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cathode
The word 'cathode' was coined in 1834 by the English polymath William Whewell at the request of Michael Faraday, who needed names for the newly discovered phenomena of electrolysis. It derives from the Greek 'kathodos', meaning 'way down', formed from 'kata-' ('down') and 'hodos' ('way'), reflecting the then-current belief about the direction of current flow in an electrolyte. Faraday also adopted Whewell's companion coinage 'anode' ('way up') at the same time. Related English words sharing the Greek root 'kata-' include 'cation', 'catabolism', and 'catastrophe'.
Related word forms
How cathode is actually used
A technical term used mainly in chemistry, physics, and electronics; it carries no emotional connotation. Note that whether the cathode is negative or positive depends on context: it is negative in electrolysis and electron tubes but the positive terminal of a discharging battery. The plural is regular: cathodes.
Easily confused with cathode
The cathode is the electrode where electrons enter (or reduction happens), while the anode is its counterpart where oxidation happens — in a battery being discharged they are positive and negative terminals respectively.