Both ŭ and j are used to make diphthongs in Esperanto: morgaŭ, homoj, Eŭropo, ejo. Yet only j is allowed in front of syllables: jam, juvelo. Why is this so?

  • One small-as-heck counterexample I can think of is "ŭo" for the name of the letter. But that doesn't really count, I think.
    – Adalynn
    Apr 24, 2018 at 0:00
  • Because it's so in Polish, German and Russian.
    – Max
    Sep 14, 2018 at 12:18

4 Answers 4


Although it is common in linguistic descriptions of Esperanto to treat j and ŭ in the same way (as glides/part of diphthongs), the phonemic system tells us not to do so, which subsequently resolves the question of initial ŭ as a kind of misunderstanding. This goes back to Zamenhof himself, who treated ŭ as if it were a consonant (in order to still be able to claim that every sound is pronounced as written and vice versa, although u and ŭ in fact are the same sound).

j is merely a consonant, so it can appear in any position that is allowed phontactically. That fact that oj in homoj may be a phonetic diphthong does not mean that it must be a phonemic one - in fact o and j do represent different morphemes here!

ŭ on the other side from a linguistic point of view is a vowel, it's the vowel u used as second part of the diphthongs and (perhaps also ). The Fundamento clearly prohibits the use of ŭ in other positions (with the exception of the name of the letter, ŭo).

The background of this can be found in the Slavic languages, which do not have inherited diphthongs (they all got monophthongised), but have the consonant /j/ and the borrowed diphthongs /au/ and /eu/.

For a treatment of this question in Esperanto see the paper by S. Pokrovskij.

  • 1
    I’m a bit confused by your logic here: 1. Zamenhof treated ŭ as a consonant, but actually (=phonetically) it is a glide (=vowel). 2. j in oj phonetically is a glide, but actually (=phonemically) it is a consonant. – – So, to me it seems that in the context of ŭ, you say ”phonetics = reality”, while in the context of j, you say ”phonemics” (?) = reality. Wouldn’t it be equally possible that j in oj (+ aj, ej, uj) is also a vowel, and that the same letter being used for a (fricative) consonant in other contexts, such as jaro, shows a fallacy in the design of Esperanto?
    – Bjørn
    Apr 25, 2018 at 7:42
  • 2
    A glide is not a vowel, but depending on the linguistic school either a kind of consonant or a mixture of vowel and consonant (semivowel); there is some impreciseness in the terminology. ŭ phonemically and phonetically is a vowel, it's just the metalanguage getting it wrong, while j phonemically is a consonant, which may be realised as a non-syllabifying vowel in certain circumstances. I'll add a link to a linguistic treatment of the topic in Esperanto. Apr 25, 2018 at 8:18
  • 1
    @CyrilRobertBrosch: I still don’t quite get the ”status difference” between J in aj and Ŭ in . To me, they both sound like glides/semivowels/whatever-you-choose-to-call-the-non·syllabic-part-of-a-diphthong. :-) I have a question for you: Does the letter J represent the same sound in the following words? kaj, kajo, kajako, kajuto, kajeto (malgranda kajo)
    – Bjørn
    Apr 26, 2018 at 12:55
  • 1
    If you include onomatopoeia, English can potentially have clicks!
    – Adalynn
    Apr 26, 2018 at 14:26
  • 2
    Nothing in the Fundamento prevents a syllabification like an-ta-ŭa. The rule to use ŭ after, and not before a vocal, does not apply to separation into syllables, but to words. And yet you can find ŭato in the online PIV dictionary as a synonim of vato and without any warning to avoid its usage.
    – Vidamuzo
    Apr 28, 2018 at 17:48

In Esperanto, J is both the offglide of a diphthong ("ŝajni") and a separate consonant ("jes"). If I remember correctly, Zamenhof was at one point considering having ĭ as the letter for the offglide letter, and just j for the other version.

Oh, and there is definitely at least one circumstance (possibly more, depending on preference/authority/whatever) where "ŭ" is in fact word initial: the name of the letter, ŭo. The questionable occurrence that I can remember is "ŭato" for the unit (Watt).

Take a look at something related in English:

  • yes = /jɛs/
  • shine = /ʃaɪ̯n/

The difference between the two /j/-like sounds in English is similar to the difference between the vowels in "bit" and "beat". Much like Esperanto's ŭ, the /ɪ̯/ sound only occurs in diphthongs.

Looking at the comments, it might be possible that initial "j" has two realizations: /j/ and /i̯/.

Hope this helps!

  • Thanks, it helps a lot! It just bothers me that the letter J is used for two different sounds, but I guess that is unavoidable. (Just like N sometimes can be heard with the pronunciation /ŋ/, as in lingvo).
    – Bjørn
    Apr 24, 2018 at 12:58
  • They sort-of do. but they're not really distinct either
    – Adalynn
    Apr 24, 2018 at 14:55
  • Clarification: J is used for the same sound (I can't recall if an offglide and the corresponding semivowel are equivalent or not, so take what I say with a grain of salt). English offglide v. semivowel are definitely distinct sounds (in theory at least).
    – Adalynn
    Apr 24, 2018 at 21:39
  • 1
    Jes is a dipthong as well.
    – Karlomanio
    Apr 27, 2018 at 17:11
  • 2
    Can you provide a reference? In every transcription of Esperanto I've seen its /jes/ not /i̯es/.
    – Adalynn
    Apr 27, 2018 at 20:57

I guess it's just the combination of a couple of things:

  • Zamenhof didn't create any “full” word with Ŭ in that position and seemed to avoid it (substituting V in most cases, except in the name of the letter and onomatopoeia, where the sound is really important and couldn't be changed to V).
  • The Eastern European languages that inspired him usually worked the same way, being biased towards V.
  • Zamenhof created the H-method where U and Ŭ look the same, so it seems that all the uses of Ŭ are supposed to be obvious (aŭ, eŭ). That wouldn't work if Ŭ was meant to appear anywhere in a word.
  • Some people consider the name of the letter to be somewhat second class. I don't understand this at all (it's OK to say that onomatopoeia may break some language rules, but not letter names).
  • There are some versions of the Fundamento that explicitly say that Ŭ should be used only after vowels and for whatever reason these versions are regarded higher (probably because it's their mother tongue, see next point). Unfortunately, they seem to be the versions I can't read (Russian and German only), so I can't check if they mandate this rule or just note the fact that other combinations don't happen. Notice that some sections of the Fundamento have some inconsistencies and can't be taken literally, you have to take them all into account. For example, the Russian version (I'm using Google Translate) seems to have several allowances for Russian beginners, such as pronouncing H and Ĥ the same and omitting the definite article, but these are not considered valid rules of the language nowadays (if they ever were). The English version says that “e” sounds like “a” in “make” (which would be “ej” in many accents) and that doesn't make the sounds “e” and “ej” equivalent in Esperanto, it was just a simplification for English speakers.
  • People see the world with their own biases, so a French or Brazilian or English guy wouldn't blink at ŭato, while a Russian or German would think “this sounds odd, it looks out of place”. Geraldo Mattos, ex-president of the Akademio de Esperanto, states that Ŭ is just like any other letter (as his personal opinion): http://host.uniroma3.it/laboratori/laat/konferencoj/2006-miljorini/Mattos-prel-eo.doc (6th page) (*)

In summary I think that syllable-initial Ŭ is not really disallowed (as proven by the letter name), it's just an uncommon sound combination, just like “bv” in Zimbabvo or “pf” in Pfenigo, and people are not very keen of changing its status in fear of making a mess of the language's phonotactics. But if a combination as uncommon as Pfenigo (a monetary unit) is allowed, then Ŭono (another monetary unit) should be allowed too, at least as a partially adapted word, because it is unavoidable when talking about the monetary unit.

Addendum: The Akademio in its recommendation about proper names (http://www.akademio-de-esperanto.org/oficialaj_informoj/oficialaj_informoj_22_2013.html) does not disallow the “Rŭando” because it's against some specific rule, but because it is “nekutima” (uncommon) and could be pronounced just like “Ruando” by many speakers (Ruando being the preferred form). The academy seems to be much more careful about mandating/prohibiting anything than most internet denizens.


[...] Multaj ne facile prononcas la konsonantajn grupojn kv kaj gv kaj tial transformas ilin respektive en kǔ kaj gǔ, sed tio estas prononco, ne skribo. La oficiala formo de la citita landnomo estas Gvatemalo.

La plej konataj vortaroj ordinare listas nur tri vortojn sub la supra litero: ǔa, ǔato, ǔo. Cherpillod (1988, p. 169) registras dek unu, inter ili la vorton ǔono.

Al la unua demando mia respondo estas klara: ne, tute ne! La konsonanto ǔo estas egala al ĉiu alia, kaj povas esti uzata antaǔ kaj post vokalo. Jen miaj argumentoj:

  1. La Franca Gramatiko bezonis nur klarigon pri la dekreskaj diftongoj, kiujn ĝi ne konas, kaj tiu klarigo aperas per germana vorto, dum la Pola bezonis nenian, ĉar ekzistas litero por tiu sono: la trastrekita lo.
  2. Estas multaj vortoj, kiuj finiĝas per tiu glitanto, sed en la Fundamento estas unu vorto, kiu komenciĝas per ĝi: ĝia nomo. Se la Fundamento mem ĝin uzas antaǔ vokalo, tia pozicio estas Fundamenta.
  3. La Ekzercaro prezentas en 2:16 la vorton majo, kiun ni devas legi ma.jo, kaj ne maj.o. El tio mi konkludas, ke la vortojn kontraǔa, kontraǔe, kontraǔi, kontraǔro kaj kontraǔu ni devas legi kon.tra.ǔa, kon.tra.ǔe, kon.tra.ǔi, kon.tra.ǔo kaj kon.tra.ǔu... Se tiuj du glitantoj komencas silabon, kohere ili rajtas komenci ankaǔ vorton!
  4. La Germana kaj la Rusa Gramatiko informas, ke tiu sono aperas post vokalo, sed la Angla, ke tiu sono formas diftongojn, kaj tio en lingvo kun multaj diftongoj: wait [ǔejt].. Diftongon tamen povas estigi ĉiu el tiuj du konsonantoj: dekreskan en la vortoj aj kaj aǔ kaj kreskan en la vortoj ja kaj ǔa. La angla instruo ampleksas la germanan.
  5. Se la Fundamento mem sin kontraǔdiras, kaj tio restas supre pruvita, ni estas tute liberaj... Mi mem ne dubas, ke nia tradicio jam akceptis la vortojn kun kreska diftongo en ĝia komenco.
  6. Se tiu posta diftongiga sono vere estus barata de la Fundamento, Zamenhof ne proponus vorton, kiu komenciĝas per ĝi: ǔa...

La respondo al la dua kaj tria demandoj dependas de la rilato inter iliaj kondiĉoj: 1. Se unu el ili enhavas la alian, mi respondas: permesata kaj deviga. 2. Se unu el ili ne enhavas la alian, temas pri konflikto, kaj ni devas turni nin al la Ekzercaro, eventuale al analogio: ĉiu elektas unu el tiuj eblecoj laǔ sia tuta bontrovo.

Se ni analizas nun la suprajn kondiĉojn por decidi pri la uzo de la glitanto ǔo, ni konstatas, ke tri el la kvin lingvoj vidas en ĝi konsonanton egalan al ĉiuj aliaj, sed du el ili ĝin restriktas al postvokala uzo: temas pri konflikto, kiun tamen la Ekzercaro de la Fundamento (1963, p. 81) solvas per kontrauzekzemplo en la fino de la unua paragrafo.

Geraldo Mattos, ex-president of the Akademio de Esperanto

  • National-language bias in our perception of Esperanto. :-) This is very interesting. I really like the phrase: Se la Fundamento mem ĝin uzas antaǔ vokalo, tia pozicio estas Fundamenta. But I guess others would disagree?
    – Bjørn
    May 1, 2018 at 8:11
  • 1
    As I usually say: if Zamenhof were really serious about prohibiting ŭ in front of syllables, he could have proposed aŭ or eŭ (or iŭ, or oŭ...) as the name of the letter!
    – marcus
    May 1, 2018 at 23:49
  • 1
    The German version of the Fundamento at akademio-de-esperanto.org/fundamento/gramatiko_germana.html says "u ― wie das kurze u in glauben (wird nur nach einem Vokal gebraucht)". This is presumably meant to be a ǔ. I would translate the parenthetical as "(only used after a vowel)" -- i.e. it seems to be descriptive rather than prescriptive.
    – Max
    Sep 14, 2018 at 12:16

ŭ in fact is a "clever" solution for phoneticising (one letter - one sound) of au and eu in national languages (av and ev would have looked bad in non-Cyrillic script). Because Esperanto intends to avoid spelling ambiguities, an independent usage of ŭ is rare. With the exception of ŭato for Watt, Volt-Ampere and for some English names like maybe Isle of Wight.

For the same reason there is no suffix -ij but -uj (for country names): the spelling would be too ambiguous, as many national language speakers would tend to (erroneously) pronounce io anyway as ijo.

The short answer would be: there already is the v for normal, full length usage of the w sound.

  • 1
    @marcus The Esperanto v is more or less a w sound. Hence vorto = word, Or do you mean the exact phonetic definition in Esperanto of v?
    – Joop Eggen
    Apr 24, 2018 at 20:47
  • 1
    @JoopEggen Indeed, ⟨v⟩ in Esperanto varies between [v] and [ʋ], the latter of which is the standard Dutch pronunciation for ⟨w⟩, while the former is the one for Dutch ⟨v⟩. So it indeed makes sense that ⟨v⟩ functions (at least partially) as a w-sound. I suppose [v] is kind of a longer and stronger version of [ʋ], but I am not sure how phonetically sound that is. At least the former is a fricative, while the latter an approximant. Apr 24, 2018 at 20:54
  • 2
    V vs Ŭ: what bothers me most is the inconsistency. You’ve got jam – maj’, varm’ – av’ but only . In other words: Both J and V can appear before and after a vowel in Esperanto, but Ŭ can only appear after a vowel. :-/ (That said, I have no problems with V as a [w] transliteration – e.g. Washington > Vaŝingtono.)
    – Bjørn
    Apr 25, 2018 at 7:31
  • 1
    @Bjørn one probably has to admit, it is a mechanism to have something like au, eu in the language; a form of synaeresis / diphthong.
    – Joop Eggen
    Apr 25, 2018 at 7:49
  • 1
    Also, had Zamenhof decided on w instead of ŭ (baldaw, Ewropo), it would probably have opened the door for lots of imports like wato, wajfajo (for WiFi) and what not!
    – Bjørn
    Apr 25, 2018 at 8:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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