My Latin teacher has said that osculum is the diminutive of os, describing the way one puckers one's mouth when kissing, and that the -culus ending is a diminutive. So what is oculus a diminutive of?

  • Welcome to the site! This reminds me of an earlier question about angulus, and it turned out it was not a diminutive. This might be the case for oculus too. I don't know what the answer to this one is, but I am eager to see.
    – Joonas Ilmavirta
    Commented Feb 12, 2018 at 1:54
  • 1
    The -c- is part of the PIE root; compare Russian око, German Auge, etc. But I'm not sure where the -ul- comes from, and it certainly does look diminutive.
    – Draconis
    Commented Feb 12, 2018 at 2:16

2 Answers 2


According to Sihler, New comparative grammar of Greek and Latin, the PIE root is *H3ekw, 'see'; according to OLD, the (theoretical) original Latin form is *oquelos. Presumably, the (u)lus that looks like a diminutive suffix is actually one of the suffixes that are added to verb roots and used to indicate instrument/means (Gildersleeve and Lodge, Latin grammar §181.6). Therefore, an oculus is 'a means of seeing' (cf. capulus, 'handle' [literally, 'a means of taking hold'], cingulum, 'girdle' [literally, 'a means of encircling']).

  • Are there other Latin words from the same PIE root?
    – Joonas Ilmavirta
    Commented Feb 12, 2018 at 10:19
  • @JoonasIlmavirta. My understanding is that antiquus is also from this root ('seen before'), but that etymology may be controversial.
    – cnread
    Commented Feb 12, 2018 at 17:58
  • I was curious, so I asked a separate question. Anyway, I am intrigued by this seemingly diminutive suffix having an instrumental function. It never occurred to me, despite the (to me very) familiar example of pendulum.
    – Joonas Ilmavirta
    Commented Feb 12, 2018 at 18:14

Indo-European *ekʷ (or h³ekʷ) is the source of the word for “eye” in many IE languages (possibly including English, though this is debated). The /l/ suffix is found only in Latin, so it is certainly possible that the Latin form is a diminutive. In this case, ocellus “little eye” would be doubly diminutive, like the words discussed here: Can there be double diminutives in Latin?

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