Vowel Quantity in Third Person Plural of Passive Voice

Question

Cārī collēgae,

The third person plural of the passive voice in the present stem has a peculiarity that I noticed a couple of weeks ago (far later than I should have, I might add) and have been curious about ever since: namely, the fact that the vowel of the penultimate syllable in a form such as spondentur (and, in general, all athematic third person plural passive forms in the present stem, including subjunctive and imperfect forms) is short rather than long – or at least, that is the case according to the work on Latin grammar used in my classes (Lateinische Grammatik by Rubenbauer & Hofmann, for reference). I tried looking it up in the work I generally like to reference when researching these types of topics – Historische Laut- und Formenlehre der lateinischen Sprache by Meiser – but was not able to find any information on that specific question, which is why I am now at a loss as to where to look next. If those of you more well-versed in the diachronic phonology/morphology of Latin know the answer to this question or are at least able to point me in the right direction, I would really appreciate it.

As it stands now, I only have the hypothesis that it might have been an analogical vowel shortening, given the shortening of spondent as a final syllable ending in a consonant other than s. From what I have read in the Ars grammatica minor by Dōnātus, for example, it seems that Roman grammarians were more inclined to view passive voice endings as explicit derivates of their active counterparts, in contrast to the practice I encountered in my school education of simply treating them as a separate system of inflectional endings; consider this quote from the aforementioned Ars grammatica minor as an illustration:

[Verba āctīva sunt,] quae in ō dēsinunt et acceptā r litterā faciunt ex sē passīva, ut lego legor.

It might therefore not be that much of a reach that spondentur was shortened in analogy to spondent – or at least, that ancient authors decided to classify the vowel as a short one, even if this did not necessarily reflect spoken language. It is interesting in light of this piece of speculation on my part that spondētur retains vowel length, but maybe also not that unexpected when you consider that shortening that vowel would have required an accent shift, whereas the penultimate syllable in the third person plural is long by position either way.

I would really appreciate any input from those of you with more knowledge on the topic – an explicit answer, a place to look for more information, or even some feedback as to whether my hypothesis is plausible would be a big help. In any case, thanks for taking time out of your day for my question, dear reader.

Answer 1

A short vowel in this position is regular, not analogical. Here is how the rules for vowel length in verb endings are described by Joonas Ilmavirta♦'s answer to How can one predict the length of theme vowels in verbs?

These cause the preceding long vowel to become short:

• word-final t
• the clusters nt and nd
• another vowel (eg. audĕō, audĭēns)

So regardless of whether the vowel was originally short or long, a short vowel is expected in this position in Classical Latin. (As you observed, although the vowel is short, the syllable is heavy, or "long by position"). Shortening of vowels before nt and nd is considered to be part of a broader sound change in Latin often described by the name "Osthoff's law" (although that more properly refers to a similar but separate change in Greek, according to Wikipedia).

In its general form, Osthoff's law states that a long vowel was shortened when followed by at least two consonants, the first of which was a resonant consonant (such as a nasal /m n/, a liquid /r l/, or a glide /j w/).

Here is a paper about it by Ollie Sayeed: Osthoff’s Law in Latin

It is unclear exactly when this law was active in Latin; there are words in Classical Latin that are hypothesized to have pronunciations that violate the law, suggesting that it stopped being active before the classical period, but there also are cases of vowels potentially being shortened in this position in the development from Classical Latin to the Romance languages, leading to a hypothesis that the law applied in non-continuous intervals, i.e. in two or more rounds (at least one before and one after Classical Latin). Here is a prior question about one alleged exception: Why is the "u" in "nuntius" and "nuntiare" long by exception?