I asked yesterday why the participle mortuus has two us. When Rafael asked whether one of the us were consonantal, I had no other evidence than being taught that they are both vocalic. Arguing by analogies is tricky as there seem to be no other verbs with the past participle stem ending in a vowel. This also makes it reasonable to conjecture that it might be /mortwus/ instead of /mortu.us/.

So, do we know how mortuus was pronounced in classical Latin? Did it have two or three syllables? Were the two adjacent us both vocalic? And most importantly, how do we know?

3 Answers 3


Here is metric evidence in support of three syllables. I went through all occurrences of mortuu- in Vergil(ius) and Ovid(ius), and I found no occurrences that would require scanning mortuus or mortuum as a two-syllable word. Such situations are possible, so absence of such evidence is evidence to the contrary. The examples below require three syllables to scan right. In addition there were cases where either reading is possible; I left those out.

  1. Vergilius, Eclogae, 3.15:

    et si non aliqua nocuisses, mortuus esses

  2. Ovidius, Amores, 3.14.40:

    tunc ego, sed tecum, mortuus esse velim

  3. Ovidius, Tristia, 3.3.66:

    sic ego non etiam mortuus exul ero

  4. Ovidius, Tristia, 4.3.47:

    denique, ut et vixi, sine crimine mortuus essem

  5. Ovidius, Ibis, 161:

    his vivus furiis agitabere, mortuus isdem

The fifth foot of hexameter is always a dactyl, and dactyl is also necessary in the second half of pentameter. There are exceptions to these rules of course, but they are observed very well in my experience of classical metric poetry. This is fairly conclusive evidence that the two adjacent us are both vocalic in mortuus in classical pronunciation.


Weiss writes that “there was no general anaptyxis between a consonant and u” (p. 145). The outcome is different and seems to be unpredictable. In some cases Cu > Cu or CC or C:

equus (*h1ekuos), Minerva (*menesua) sollus (*soluos); probus (*probhuos), suavis (*suaduis);

Weiss 2009/2011 adds that “*tu apparently did become *tuu with gemination of the t if it was in the coda” (p. 145):

*mor.tuos > mortuus (no gemination of t) but *kwat.uor > quattuor (geminated t)

De Vaan adds that “the change from PIE *mrtuo- to *mrtuuo (conditioned by t?) was PIt.” (p. 390).


According to Yellow Sky's description (which lacks citations but lines up with all the words I can think of), the suffix -vus (from PIE *-wós) has three different forms:

  • -vus after A, E, I, O, L, or R
  • -us after U or V, including QV
  • -uus after anything else

Since mort- ends with a T, it falls into the "anything else" category, and the two-syllable suffix -uus is used.

  • Do you mean that /-twus/ is impossible in Latin or is this specific to the suffix -uus? If it only concerns the specific suffix, one also has to argue why this participle comes from it.
    – Joonas Ilmavirta
    May 14, 2018 at 16:58
  • 2
    @JoonasIlmavirta I seem to remember /w/ → /u/ in general after non-resonants, though I'll need to find a source on that.
    – Draconis
    May 14, 2018 at 17:59

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