Is there an explicit reason for -o, -a, -e, -i? The longer ones vaguely remind me of similar words/constructs in different languages that influenced Esperanto, but the very basic ones seem completely random. Is there an origin story for this choice?

  • 1
    I wanted to mention that Zamenhof experimented with different vowls prior to the released Esperanto. So it might be a matter of taste. Also who knows: -a for nouns, -o for adverbs are maybe too slavic, or -o being too ugly for anything else than noun? Personally I think the adverb-adjective-noun hierarchy (noun most prominent) is finely served by -e -a -o. That endings start with a vowel is but practical for chaining word parts.
    – Joop Eggen
    Commented Sep 4, 2018 at 13:45

1 Answer 1


Interestingly, Wiktionary has an etymology for all of these:

  • -o:

From the masculine singular of the Romance languages, such as Italian (amico); perhaps also the neuter singular of Russian (окно (okno))

  • -a:

From feminine singular adjectives (and nouns) of the Romance languages, such as French ma, Italian mia, Spanish mía, fría.

  • -i:

Perhaps from Latin deponent verbs such as loquī (“to speak”).

  • -e:

From the Latin and Italian adverbial suffix -e (as in bene "well"), perhaps reinforced by the Russian adverbial -e found after a palatalized consonant.

However, none of them have a citation and they don’t really seem particularly convincing. For example, in Spanish the -o ending is also used for masculine adjectives and the -a for feminine nouns so the hypothesis doesn’t really make a lot of sense.

My hunch is instead that Zamenhof just wanted to use all of the vowels for the endings because they are short and can be easily pronounced after most sounds. The actual meaning which they are each assigned is probably mostly arbitrary.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.