Latin has quite a few words with -oe-, such as Poenus and moenia. But I've heard it said that all of those words are either translitterations from Greek -oi- or adopted from non-standard dialects of Latin (although I thought the Romans seldom passed on a chance to standardise variants, which is why Latin spelling is so uniform, compared to e.g. Greek or Mediaeval Dutch?). Is this true?

Bonus questions:

  • Are there other origins of -oe- in Latin than the two mentioned above?

  • Was -oe- used more frequently in pre-classical Latin?

  • @sumelic: Yes, exactly, standard would be -u- (cf. Poenus, Punicus). But I thought it was just regional, not originally from Rome (so I was probably wrong). I know one/an was something with oin- in Proto-Indo-European: so you're saying pre-classical Latin also had this oi- in what would become unus? If so, that would be the stub of an answer to my two bonus questions...
    – Cerberus
    Commented May 17, 2016 at 2:50
  • 1
    Rudolf Walter (Walter 1987, Altlateinische Inschriften) writes that oe "was nichts anderes ist als eine graphische Neuerung für altes oi und in der Kaiserzeit /e/ ausgesprochen wurde" (p. 316). He also argues that when and how this "archaizing" spelling innovation became regular "ist nicht feststellbar."
    – Alex B.
    Commented May 17, 2016 at 5:04
  • Which for those who don't know German means "impossible to determine." :) @AlexB, any chance you could convert this into an answer? Commented May 17, 2016 at 9:14
  • Sihler par. 59 discusses the origin of Latin oe in detail. The question is debated.
    – fdb
    Commented May 17, 2016 at 9:21
  • @AlexB.: Oh, that's interesting. But he doesn't say whether there used to be any -oi- words (before this innovation) that were neither Greek nor dialectical. Or are we to interpret him thus?
    – Cerberus
    Commented May 17, 2016 at 11:33

2 Answers 2


This answer is based on the discussions in Weiss and Sihler.

The regular development is oi > ū: e.g. ūnus : Gk. οἴνη "one (on a die)". There are inscriptions up until the second half of the 2nd century BC that still show OI, e.g. LOIDOS for later lūdus.

However, there are a few words that have oe instead of ū: e.g. moenia, poena, Poenus, foedus "ugly", foedus "treaty". In all of these words the oe is preceded by a labial and followed by a coronal. (In other words with oe, e.g. coepī, proelium, the oe is secondary and results from the combination of a prefix ending in -o with the vowel e.) But, apparently it is not a question of simple phonetic conditioning, as Weiss says that "this cannot be the whole story since evidently oe did monophthongize in this environment in some words". Examples include some words from the same roots as the words above, e.g. Pūnicus, mūnīre. Sihler mentions the theory that the words which retained oe are "technical or literary" words, but this does not seem to be true of all of them. Neither Weiss nor Sihler mentions the possibility that these words are loans from a non-standard dialect.

So it looks like there's no complete answer: the outcome oe is partly phonetically conditioned, but there may be something more going on that we haven't figured out.

  • Excellent answer, merci! I have heard someone say the oe in some words has a dialectical origin, but I don't remember who. It must have been a professor or other university teacher. As to "this cannot be the whole story since evidently oe did monophthongize in this environment in some words", cf. Poenus, Punicus and moenia, munio: in both cases, we have oe and u from the same root. Only dialect and accentuation come to mind as potentially differentiating factors, besides—don't make me say it—chance.
    – Cerberus
    Commented Jun 13, 2016 at 0:38
  • Oh, of course you're right about Pūnicus, mūnīre being among the exceptions -- Weiss actually mentions these; don't know how I missed it. Editing the answer accordingly.
    – TKR
    Commented Jun 13, 2016 at 0:55
  • Perfect! An punio. I'm still thinking of either archaicisms or dialecticisms. Or perhaps those are the same thing in this case. Incidentally, L&S has a few tantalizing bits of information: foedus, ĕris (for foedus, Ennius wrote fidus, acc. to Varr. L. L. 5, 86 Müll.foedus, a, um, adj. [Sanscr. dhūmas, smoke; cf.: fumus, fīmus, feteo]. Ablaut?
    – Cerberus
    Commented Jun 13, 2016 at 2:34
  • Foedus~fidus looks like it could easily be an ablaut alternation. The connection with Skt. dhūmas seems less clear (etymological notes in L&S are generally not very reliable, likewise for LSJ etc.).
    – TKR
    Commented Jun 13, 2016 at 2:44
  • I was too lazy to get De Vaan...
    – Cerberus
    Commented Jun 13, 2016 at 16:49

It appears that while the oe diphthong was common among words that came from dialects of Latin and/or Greek assimilations, other words exist that appear to be native to Latin. Take coepio (to begin), for instance. It is a very common word that has been in use seemingly since the beginning of the language. It was used all over, so it is not generally dialect-specific. Although it may have been more common in the sources you mentioned, it was also a natural entity.

  • That is a very interesting example! It does seem to be a contraction of co-apio, often read as two syllables (coëpi) in older Latin, but perhaps that doesn't disqualify it: archimedes.fas.harvard.edu/cgi-bin/… I'm having trouble deciphering Lewis & Short's "v.a. and n.", though. Verbum activum and noun? Vide ante and neuter? Vox activa? The abbreviations: latinlexicon.org/LNS_abbreviations.php
    – Cerberus
    Commented Jun 11, 2016 at 22:54
  • @Cerberus I'm also having issues with those abbreviations... It can't be noun or neuter because those refer to nouns and this is a verb. It also can't be vide ante as that means "see before" which makes little sense in context. Interesting...
    – Sam K
    Commented Jun 11, 2016 at 23:24
  • @Cerberus I believe they mean "verb active and neuter", which are old-fashioned terms for transitive and intransitive.
    – TKR
    Commented Jun 12, 2016 at 5:04
  • @TKR: Ahh that does make sense! I should have looked it up.
    – Cerberus
    Commented Jun 14, 2016 at 2:39

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