This question inspired the following: I should verify whether the prefix really means something. I quoted the French version of Wiktionary because the English version does not state the Latin etymons (only the PIE etymons).

De l’indo-européen commun *u̯er- [1] (« couvrir » → voir veru) avec le préfixe op-,
plutôt qu'un dérivé [2] de pario. Voyez son antonyme aperio.

  • 2
    Please don't ask multiple nearly-identical questions. Also, stems can include things that look like prefixes. That's good Latin.
    – anon
    Commented Feb 29, 2016 at 3:32
  • 2
    Actually, operīre and perīre aren't related, at least not in the way this question assumes. The former is a fourth-conjugation verb (operiō) and the latter is an irregular verb in the same pattern as īre (pereō). Commented Mar 2, 2016 at 3:21
  • It seems that aperio is the anthonym by means of a+operio, where either the o was elided in the process, or was undergoing aphaeresis at the time aperio formed. The corresponding Proto-IE root lists an initial vowel as optional. If that is true, there would be no prefixes.
    – Rafael
    Commented May 20, 2016 at 17:41
  • @Rafael Thanks. Please feel free to edit my question if the quote is wrong.
    – user37
    Commented May 22, 2016 at 3:17
  • The quote seems right. It is just that when there is disagreement between wiktionary and a primary source, I think the primary is preferable
    – Rafael
    Commented May 22, 2016 at 12:41

1 Answer 1


The prefix op- originated ob- (e.g. obsto from *opsto), and is visible in operio (< *op-u̯eri̯ō) and oportet.

The verb derives from PIE *su̯er-, which means "to close, cover" or "to guard, save".

Given that aperio (< *ap-u̯eri̯ō), which means "to open", is formed with the prefix ap-, "from, out" (ancient Greek ἀπό), and at the opposite op- means at, by, around, round about, all around (ancient Greek ἐπί), in the case of operio the prefix could denote that the object is completely closed or enclosed.

For further references see the digital edition of the Indo-European Etymological Dictionary of Pokorny-Lubotsky (use the "find" function of the browser and search "aperi" or "operi").

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