There are many particle names ending in -on in English: electron, muon, lepton, proton… How should these particle names behave in Latin?

My impression is that the electron and the proton came first (I'm not sure of their naming order), and the rest were modeled on them. The electron is "amber" (ἤλεκτρον) and proton is "first" (πρῶτον). This makes me want to treat all these particles of second declension neuters of the Greek type, and I wouldn't be opposed to Latinizing them into electrum and protum if someone is so inclined.

However, Vicipaedia seems to treat these words as third declension masculines ending in -on/-onis. This feels off to me, especially with the final -n which I expect to be dropped from a Latin nominative of this kind. The Latin Wikipedia is not particularly reliable, but there might be a good reason for this convention. Perhaps the words were borrowed from English to Latin and assigned to the third declension without much etymological thought. Or this might be by analogy to Italian where the ending is -one (corresponding to the Latin third declension).

Etymological considerations and comparison with Italian seem lead to different Latin declensions. Vicipaedia also gives the alternative electronium. Yet another thing to consider is that the neutron might have a significant conflict with the pronoun neuter.

How do you think the particle names ending in -on in English should be treated in Latin? And, most importantly, why so?

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    The -on/-onis ending seems off to me too. I'd have thought electrum, protum, etc. would be the most obvious Latin forms. Perhaps it's merely to distinguish the word for electron from the word for amber, and then the other particles are named by analogy. I'm not sure that's a very compelling reason though; after all, how often does the word amber really come up? On a whim, I checked what the modern Greek words for electron and proton are, to see whether they've also been distinguished from the words for amber and first. Sure enough: ηλεκτρόνιο and πρωτόνιο, which I assume are diminutive forms.
    – cnread
    May 23 '17 at 21:48
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    @cnread Vicipaedia also gives the alternative electronium (which I only now remembered to add to the question). Many words have several different meanings, and the risk of confusing electrons with amber is minimal. If it seems to be a problem in some situation, one can always add words to clarify. I wonder if the suggestions in Vicipaedia are borrowed from (written by native speakers of?) Italian or Greek. I feel it's best to go directly from the Greek origin to Latin without passing through modern languages, but others might disagree.
    – Joonas Ilmavirta
    May 23 '17 at 21:57
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    Based on cursory (cough Etymonline cough) research, the "-on" in electron is by analogy with "ion," which itself is merely a transliteration ἰών, the present participle of Greek "to go." In that case, it would be misguided to act as if -on was a neuter 2nd declension ending. I found an old book called De iontum migrationibus electrolyticis to confirm that at least one person thought that way...
    – brianpck
    May 24 '17 at 0:47
  • The rule on Vicipædia is "noli fingere": they want a source or precedent for every word. Are you able to check the sources given in the Vicipædia article? (They're at the bottom in small type under Notae.)
    – Ben Kovitz
    May 24 '17 at 0:48
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    Everyone: There are very good observations and nice ideas in the comments. Please write your ideas into answers. An answer does not have to be perfect to be useful. I would much like to have the different ideas posted as answers, so that people can vote, comment, and develop the ideas further.
    – Joonas Ilmavirta
    May 24 '17 at 4:20

It is correct that ἤλεκτρον means “gold-silver alloy”, and then “amber”, and that it is the source of modern words like electricity, electric, electromagnetism etc. But I do not think you can say that “electron” is borrowed directly from ἤλεκτρον, especially as it does not have the same meaning. Rather it is a modern formation with the “particle” suffix -on. This started with the genuine Greek words anion “going up” and kation “going down”, both neuter participles of the verb “to go” with different prefixes: an- and kat(a)-. Then we got “ion” on its own as a term encompassing both, and then, by analogy, “proton”, “electron”, “neutron”, and ultimately also “positron” (the last of these based on a spurious reanalysis of electr-on as elect-ron, and creation of a pseudo-suffix “ron”).

So what to do in (Neo-)Latin? Perhaps reborrow the English “electron” as electron, -ontis?


To add another voice to this conversation, I would like to show the entries given for various particles in the Morgan and Silva Furman University Lexicon:

electron- electron, -onis; electronium, -i

proton- protonium -i

neutron- neutro, -onis; neutronium, -i

anti-neutron- antineutronium

anti-proton- antiprotonium

photon- photonium

quark- quarcium

For the most part, there seems to be a trend of adding -ium to the end of the particle's English name. Many of these words are source to the Latinitas Recens, so it seems somewhat credible. However, as for electron and neutron, there seems to also exist alternative forms that retain the more Greek origins. fdb suggests in their answer that the genitive form for this would be -ontis, however, this seems to be refuted by these entries, which drop the t. Joonas Ilmavirta makes a good point about how some of these terms may be confusing when one starts talking about other similarly named objects, but I feel as though, to use his example, protonium would not be translated as such. In the Wikipedia article he cites, it states that the other name for this particle is anti-protonic hydrogen. Perhaps this could instead be translated as antiprotonicum hydrogenium. Note here that even hydrogen follows the -ium rule.

It seems that there is evidence for -ium as the preferred ending to particles. However, there is still much to be discussed in the matter, as demonstrated by the many comments and answers to this question.

A few final notes:

  1. There are a few deviants to this pattern that I found, one of which was already discussed:

ion- ion, iontis

neon- neon, neoni

I'm not sure what to make of that, but I guess that's for you to figure out.

  1. Even in classical Latin there are examples of words that look exactly the same, and yet have different meanings. Although attempts should be made to avoid this moving forward, it is something we still have to deal with if it does occur. Just one example:


  • nominative or genitive singular meaning bird
  • dative or ablative plural meaning grandmothers/fathers

Obviously, the meaning could probably be deduced from context, and I think a similar line of thought could be used when talking about possible conflicts. So those are my two cents, do with that what you will!


There are reasons to treat them as (Greek style) second declension neuters. The Latin ending corresponding to the Greek -on is -um, and the names can be Latinized as electrum etc.

There was no word for an electron in Greek or any other language. One simply had to come up with a new word or borrow a word from a classical language and change the meaning — the latter method was certainly not unheard of in science. Picking ἤλεκτρον for the name of a negatively charged particle makes sense. Similarly πρῶτον can be chosen for the name of a positively charged particle.

These two words are second declension neuters in Greek, and are easily recognized as such. (Yes, πρῶτον has masculine and feminine words too, but the neuter forms are regular second declension.) Therefore it is most intuitive to treat them similarly as Latin words.

Similarity to the Greek participle ion may be seen as an accident. I see no problem declining ion as iontis while using the genitive electri for electron.

I would strongly advise against using forms like electronium, since there are established physical concepts with names like protonium. When confusion can be avoided, it should.


My understanding is that the mother of all -on scientific terms is the ion, which is a Greek neuter participle (I'm told). Later -on coinings seem to be a play on the already understood word ion. It's natural Latinization, it seems to me, would be ion, iontis.

Mutatis mutandis, then, the genitives of your list of words would be electrontis, muontis, leptontis, protontis, etc.

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