The country name Australia is Aŭstralio in Esperanto, not just Australio. Another example is ambaŭ.

For me, it looks weird because just spelling as Australio would sound the same as Aŭstralio.

Why would there be an unnecessary breve on 'u'?

  • It is a shortcut w.
    – Joop Eggen
    Commented Feb 23, 2023 at 9:30

3 Answers 3


Any Esperanto basic course would give you the answer.

A longer answer.

There are a couple of grammar and pronunciation rules that come to play here.

  • There are just five vowels: a, e, i, o and u.
  • Every syllable has exactly one vowel.
  • The word stress always lays on the second last syllable.
  • The word stress is marked by prolonging the vowel.

These result in that there are no (written) long vowels (like in the German word ein Paar, a pair) and no diphthongs, i.e. two different vowels (like in ther English word "pair"), in a single syllable. However lack of these imposes quite a limit on possible syllable combinations, so therefore Zamenhof introduced two half-vowels, duonvokaloj j and ŭ.

la duonvokalo j

The letter j actually plays a double role. We have the normal j at the front of a vowel: jaro, kajako etc. This is pronounced as [j].

Then we have the half-vowel, also written with j, which forms diphthongs with preceeding vowels a, e, o and u belaj, hejmo, domoj, tiuj etc. These combinations are pronouced without a pause, as vowel + [i].

la duonvokalo ŭ

In contrast the letter ŭ always denotes a half-vowel, that is it always forms a diphthong with the preceeding vowel. There is a strong tradition to have only the diphthongs of and , e.g. Aŭstralio resp. Eŭropo (see for instance Should we create new words with "oŭ"? here in Stack Exchange).

other vowel combinations

Because only j and ŭ can form diphthongs every other combination of two vowels mean that vowels belong to different syllables. To mark this in speech there should be a short pause between those vowels, e.g. in the word duonvokalo between the u and o. Having said that especially in the correlatives like tiuj ⟨ti.uj⟩, this pause can be extremely short.

  • 1
    Now I understand why the word 'kuiras' pronunciation is separated between 'ku' and 'iras' when I learn in Duolingo. Thank you for the great explanation.
    – user67275
    Commented Feb 24, 2023 at 0:37
  • Is there a reason people call it a dipthong only when the vowel comes first? The way I learned it, ja and aj are different realizations of the same phenomenon: a diphthong. For example, we don't say that the S in "sa" and "as" represent different sounds they're just small variations of S.
    – marcus
    Commented Feb 28, 2023 at 19:14
  • A diphthong means two different vowels in the same syllable. Thus aj, ej, oj and uj are considered diphtongs in Esperanto, since they are pronounced as [ai], [ei] , [oi] resp. [ui]. When the letter j stands before a vowel, it is pronounced as [j], i.e. as a consonant, and thereby ja, je, jo and ju are not diphthongs. Note, there are no words with the ij diphthong (except direct loans), while ji is a frequent syllable. Commented Mar 1, 2023 at 8:03
  • But "ia" in one syllable is the same thing as "ja" and "ai" in one syllable is the same thing as "aj"... How could they sound different (without making j into ĵ ofc)?
    – marcus
    Commented Mar 4, 2023 at 16:55
  • In my native language i and j represent different sounds (i is a vowel while j is always a consonant), So you pronounce ia and ja differently. The situation can be different in other languages. Zamenhof was aware of this, so he decided that only those two half-vowels can form diphthongs, i.e. ia and ai cannot be in one syllable. Commented Mar 5, 2023 at 12:26

For the ambaŭ example the pronunciation would definitely change if it was spelt ambau because the is considered a single syllable and Esperanto has the rule that the stress is always on the second-to-last syllable. So ambaŭ is pronounced like AMBaŭ whereas ambau would be like ambAu.

I think in the case of Aŭstralio the pronunciation is still subtly different than Australio because the is a diphthong which means the two sounds are combined into a single syllable, ie, the mouth glides from one sound to the other in the space of a single syllable. However in practice I imagine when people speak quickly the au sound would become anyway. That is probably why that combination is extremely rare in Esperanto. I can only think of examples like praulo, but again in that case the letters are part of the second-to-last syllable so it has a very distinct pronunciation like praUlo.


Yes, it is never fully articulated as u or English long oo. It is part of diphthong whose pronunciation ends before the oo sound is reach by the tongue. The end-sound is rather like closed -uh like the u in "purview". The same remark must be made for j. It never reaches, especially in a falling diphthong the full pronunciation of i or long ee. The end-sound is rather the sound of final e in "decided" or i in "will". It never reaches the full i-sound of Esperanto. This must be noted when pronouncing the uncustomary diphthong ujn which must rhyme with "ruin" (when uttered slowly) not "ruing". It would be better to teach these semi-vowels ŭ and j as different vowels of their own kind, albeit always least stressed, rather than as a mere shorter version of u and i.

The proof of it is that in English the w is clearly distinctly heard before oo and in wood, would, woo. If it were a shorter u one would hear ood, ould, oo. It definitely starts with a kind of closed uh (a central closed or mid-closed vowel).

  • It's traditional to use /ɪ/ and /ʊ/ instead of /j/ and /w/ for diphthongs in English and simple /u:/ for English long oo, but that approach is too English-centric and doesn't necessarily apply to Esperanto, and not only that, those symbols are wrong for English too: youtube.com/watch?v=gtnlGH055TA
    – marcus
    Commented Oct 18, 2023 at 15:44

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