The usual Latin diminutive suffix is -ulus (or -ula or -ulum). However, it sometimes appears as -olus, like in filiolus, aculeolus, petiolus, and bestiola. (And perhaps Venezuela, Venetiola, is a small Venice.) When is -olus used instead of -ulus? It seems that a vowel is followed by -olus and a consonant by -ulus, but I have not seen this rule explicitly stated. Does some grammar describe the choice of the diminutive suffix?

Background: I read recently about a children's parliament (which promotes children's ideas and teaches them the basics of democracy), and I wondered what I would call it in Latin. I thought a diminutive of curia would be a nice translation. Trying to attach -ula to curia produced curiola, as my intuition immediately rejected curiula. The problem is that I have no idea why I thought so. Therefore I would like to know how the vowel (o/u) is determined.

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    There is also -culus, and -unculus (where c and unc do not add anything, but are consistently used to form diminutives. This page also says -lus itself is used. Sorry for the lame sources, but I think they might add something to the discussion
    – Rafael
    Commented Mar 16, 2017 at 15:24
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    @Rafael I know that -ulus is not the only diminutive suffix. I just wanted to focus the question on comparing -ulus and -olus. I would certainly want to know more about the -(un)c- before -ulus, but that should go to another question. (Feel free to ask!) I'm not sure I buy the -lus suffix, especially if the only example is porc-ulus.
    – Joonas Ilmavirta
    Commented Mar 16, 2017 at 15:36
  • Gobius can be named "Gōbulus" (Name of a gobie native to the Atlantic and Pacific coasts of the Americas), "Gobiusculus", the two-spotted goby. And perhaps, for sure, "Gobiōlus". I think the preference is 'flattering' towards -olus, in words finished in -is/ -es (iolus, eolus), being overwhelming in popular latin
    – ephesinus
    Commented May 23, 2021 at 8:52

2 Answers 2


A word search confirms that -olus is used instead of -ulus after a vowel.

A Perseus search for words ending in -olus reveals (among a few false positives, like malevolus) that every diminutive form follows a vowel. A similar search for -[vowel]ulus, such as -iulus, only returns false positives.

This is confirmed in Allen and Greenough's Latin Grammar:

[Diminutives] are formed by means of the suffixes -

-ulus (-a, -um), -olus (after a vowel), -culus, -ellus, -illus


As brianpck says, after a vowel only -olus is possible (and -ulus is not).

One other place where -olus can appear is after V (consonantal U) or QU, since a general habit in older Latin documents was to write O instead of U (V) after these consonant sounds. (It's not clear whether this O represented the sound /o/, or was just a different spelling of the sound /u/.) E.g. parvolus and servolus exist as variants of parvulus and servulus, and the forms equolam and aquolam can be found in Plautus.

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    And the name Scaevola, although like with parvolus and servolus about, it was also written Scaevula.
    – cmw
    Commented May 15, 2021 at 11:21

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