Editing Cathode (section)

==Etymology==
The word was coined in 1834 from the [[Greek language|Greek]] κάθοδος (''kathodos''), 'descent' or 'way down', by [[William Whewell]], who had been consulted<ref>{{cite journal |last=Ross |first=S |date=1 November 1961 |title=Faraday consults the scholars: the origins of the terms of electrochemistry |journal=Notes and Records of the Royal Society of London |volume=16 |issue=2 |pages=187–220 |doi=10.1098/rsnr.1961.0038 |s2cid=145600326 }}</ref> by [[Michael Faraday]] over some new names needed to complete a paper on the recently discovered process of electrolysis. In that paper Faraday explained that when an electrolytic cell is oriented so that electric current traverses the "decomposing body" (electrolyte) in a direction "from East to West, or, which will strengthen this help to the memory, that in which the sun appears to move", the cathode is where the current leaves the electrolyte, on the West side: "''kata'' downwards, '''odos'' a way; the way which the sun sets".<ref>{{cite book |last=Faraday |first=Michael |year=1849 |title=Experimental Researches in Electricity |volume=1 |url=http://www.gutenberg.org/files/14986/14986-h/14986-h.htm |location=London |publisher=University of London |author-link=Michael Faraday}}</ref>

The use of 'West' to mean the 'out' direction (actually 'out' → 'West' → 'sunset' → 'down', i.e. 'out of view') may appear unnecessarily contrived. Previously, as related in the first reference cited above, Faraday had used the more straightforward term "exode" (the doorway where the current exits). His motivation for changing it to something meaning 'the West electrode' (other candidates had been "westode", "occiode" and "dysiode") was to make it immune to a possible later change in the direction convention for [[electric current|current]], whose exact nature was not known at the time. The reference he used to this effect was the [[Earth's magnetic field]] direction, which at that time was believed to be invariant. He fundamentally defined his arbitrary orientation for the cell as being that in which the internal current would run parallel to and in the same direction as a hypothetical [[solenoid|magnetizing current loop]] around the local line of latitude which would induce a magnetic [[dipole]] field oriented like the Earth's. This made the internal current East to West as previously mentioned, but in the event of a later convention change it would have become West to East, so that the West electrode would not have been the 'way out' any more. Therefore, "exode" would have become inappropriate, whereas "cathode" meaning 'West electrode' would have remained correct with respect to the unchanged direction of the actual phenomenon underlying the current, then unknown but, he thought, unambiguously defined by the magnetic reference. In retrospect the name change was unfortunate, not only because the Greek roots alone do not reveal the cathode's function any more, but more importantly because, as we now know, the Earth's magnetic field direction on which the "cathode" term is based is subject to [[Geomagnetic reversal|reversals]] whereas the [[electric current|current]] direction convention on which the "exode" term was based has no reason to change in the future.

Since the later discovery of the [[electron]], an easier to remember, and more durably technically correct (although historically false), etymology has been suggested: cathode, from the Greek ''kathodos'', 'way down', 'the way (down) into the cell (or other device) for electrons'.