Google says "proton" is from "protos" and "-on" ("first" + "being"), or "πρῶτος" and "?". What is the "-on" in Greek, is it "ὤν" or "ἐν" or something?

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    But this is an English site, not a Greek site … – Jason Bassford Oct 27 '19 at 21:04
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    Ancient Greek is normally treated at latin.stackexchange.com or the etymology can also be asked at linguistics.stackexchange.com – Vladimir F Oct 28 '19 at 7:41
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    Folks, this is an English etymology question alright. – Kris Oct 28 '19 at 12:03
  • As John Lawler observes in a comment beneath the accepted answer, the '-on' suffix in electron (and in argon) is '-ον' (omicron nu). – Sven Yargs Oct 29 '19 at 1:22

-on, from ion, Greek present participle of ienai (go)


coined 1891 by Irish physicist George J. Stoney (1826-1911) from electric + -on, as in ion.

ion (n.):

1834, introduced by English physicist and chemist Michael Faraday (suggested by the Rev. William Whewell, English polymath), coined from Greek ion, neuter present participle of ienai "go," from PIE root *ei- "to go." So called because ions move toward the electrode of opposite charge.


  • Can you please write it in greek script, that's the main thing I am looking for. – Lance Pollard Oct 27 '19 at 20:27
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    No, it's omicron nu. The Greek -on singular neuter is cognate to the Latin -um singular neuter; the plural neuter for both languages is -a (alpha in Gk). – John Lawler Oct 28 '19 at 2:25
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    And here I thought electron was already the Greek word for amber – Hagen von Eitzen Oct 28 '19 at 9:43
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    @LancePollard If it's super-important that the answer uses Greek script, this really doesn't look like a question about English. – David Richerby Oct 28 '19 at 10:28
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    @user067531 Sorry, which is it? present or past? Your second quote conflicts with your own wording at the top of the answer. – TylerH Oct 28 '19 at 17:47

Here's the Oxford English Dictionary's etymology for the ending -on:

-on (in electron n.2, itself after earlier ion n.), reinforced in both senses by -ον as a termination of Greek neuter nouns and adjectives and their derivatives, and (especially in sense 2) perhaps by ancient Greek ὄν being (compare -ont comb. form).


  • "Sense 2" is in words like chronon, virion, and codon which are "entities conceived of as discrete or basic units".
  • -ont is used in words like planont.

Michael Quinion, Ologies and Isms: Word Beginnings and Endings (Oxford, 2002) breaks its coverage the suffix -on into two entries, starting with this one:

-on1 Subatomic particles or quanta; molecular units. {Originally from electron, probably from the ending of ion and influenced by Greek on, being.}

An electron a a stable subatomic particle with a negative charge. On its model, -on has become the dominant ending with which to label elementary particles and groups of such particles (for another see -tron); ...

Quinion then lists English examples of this line of derivation from the subcategories of particles (proton, meson, baryon), quanta (photon, graviton, phonon), and molecular biology (codon, intron, operon). But that doesn't exhaust the universe of Greek-derived English words ending in -on. Quinion follows with this entry:

-on2 Inert gases. {The Greek neuter ending -on.}

Argon was the first of the inert gases to be discovered; its name was taken from Greek, the neuter of argos, idle, from a- without, plus ergon, work. Others were named in imitation: neon (Greek, literally 'something new', neuter of the adjective neos), krypton (Greek krupton, neuter of kruptos, hidden); xenon (Greek, neuter of xenos, stranger); radon (from radium).

Merriam-Webster's Eleventh Collegiate Dictionary (2003) gives first-occurrence dates of 1891 for electron and 1894 (argon), 1898 (neon, krypton, and xenon), and 1918 (radon) for the inert gases. The odd gas out here is helium, which was named in 1872 and somehow avoided being retroactively renamed helion. As for ion, the possible inspiration for electron, it dates to 1834.

Whether the inert gas names starting in 1894 were influenced by the slightly earlier emergence of electron (in 1891) is a matter of conjecture, but as Quinion shows, the term a-ergon has solid etymological legitimacy in its own right—and the particulate sense of the ion/electron family of words is unmatched by the gases except under a very powerful microscope.


-ον is the ending of most neütral adjectives (in the singular nominative). πρῶτος is masculine, πρῶτον is neütral.

The neütral present participle ὄν (being) of εἶναι (to be) is also an adjective ending in -ον, but plays no rôle in explaining the form πρῶτον. Similarly with ἴον (going), in spite of the accepted answer.

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