essentially i am doing an assignment for class in which we are building a pretend vowel system for a pretend language based on sound files we are given. i had two diphthong files with 5 other files that were isolated vowels. the sounds in the diphthongs were different from all of the vowel sounds i was given.

obviously it is a fake language with a fake phonetic system but it got me thinking if anyone knew any languages that had this phenomena ? A language that has sounds occurring in diphthongs that don’t occur outside the diphthongs as their own vocalic sound.

It’s possible that a language like this is impossible but I was just curious

  • You're looking for examples like having /aw/ but not /w/?
    – Draconis
    Nov 11, 2020 at 4:42
  • yeah something like that !
    – user28146
    Nov 11, 2020 at 4:46
  • I think there are lots and lots of languages which have diphthongs that consist of sounds that may be identified with existing simplex phonemes, but whose actual production do not match any simplex phonemes. Examples from English have already been given; similar examples from other languages could easily be adduced: Faroese <ú> is [ʉu] when long, and there’s no phoneme /ʉ/; Irish has /uə/ as a diphthong, but only /ʊ/ as a short monophthong; Mandarin only has [ɛ] in diphthongs with /i/, though it’s usually analysed as being the existing phoneme /ə/, etc. Nov 12, 2020 at 18:10

4 Answers 4


Attic Greek lacked /w/ and /j/, but had diphthongs /aw/, /ew/, /aj/, /oj/.

(It also lacked a short /u/, if you prefer to write /au eu/.)

  • In the case of /j/, it seems obvious that the diphthongs should be analyzed /ai/ /oi/ and not /aj/ /oj/ because 1) it would force you to posit an otherwise unused phoneme (even though this is apparently the case for /u/) and 2) since it never behaves as a consonant, the phoneme should be a vowel, not a consonant (which is true for /u/ vs. /w/ as well)
    – b a
    Nov 12, 2020 at 15:34
  • @ba As far as I know, though, the diphthongs always behave as single units rather than as two vowels next to each other. We also see a diachronic shift of /u/ → /y/, which didn't affect the second half of diphthongs; you could say that shows one phoneme /u/ splitting into two /u y/, one of which only appears after /a/ and /e/, but that doesn't seem any simpler than positing /w/ only in diphthongs to begin with.
    – Draconis
    Nov 12, 2020 at 23:29
  • @ba Re never behaves as a consonant—it never quite behaves as a vowel of its own either, though. That is, it's never the nucleus of its own syllable, because a diphthong acts as a single nucleus.
    – Draconis
    Nov 12, 2020 at 23:31
  • On the first comment: this doesn't seem to pose a problem, because 1) diachronic shifts in principle shouldn't decide how you analyze the synchronic phonology because they can create new phonological systems; 2) even if you do take it into account, the /u̯/ in a diphthong isn't pronounced the same way as the full vowel /u(:)/, so a different development is understandable; and 3) on the subject of diachronic shifts, is it easier to say that some /w/ were deleted and some were not, or /w/ was deleted and /u̯/ was not (and some /w/ were reanalyzed as /u̯/)?
    – b a
    Nov 13, 2020 at 0:59
  • 1
    @ba Oh, don't get me wrong, my preferred analysis for Attic Greek would just treat the diphthongs as atomic units at the phonemic level. I think adding additional phonemes which can't stand on their own, only in diphthongs, seems unnecessarily complicated. That analysis just isn't useful for the OP.
    – Draconis
    Nov 13, 2020 at 1:26

RP has [aɪ] and [aʊ] but no [a]. Phonemically you could analyse these as /æɪ/ or /ɑɪ/, or /æʊ/ or /ɑʊ/ respectively though

  • If you get a little more specific, the first parts of the /aɪ/ and /aʊ/ diphthongs are also not identical – the one in /aɪ/ is more retracted and closer to /ɑ/, and the one in /aʊ/ is more fronted and closer to /æ/. Nov 19, 2020 at 15:34

Standard Mandarin's monophthongs in the usual five vowel analysis /i, u, y, ə, a/ (Pinyin i, u, ü, e, a) [and even if you include the apical vowel /ɨ / or /ɹ̩~ɻ̩/ or /z̩~ʐ̩/, Pinyin i] mean that /o/ and /e/ are only present in diphthongs /ou̯, jou̯, wo, je, ɥe, ei̯, wei̯/ (Pinyin: ou, iou, uo, ie, üe [xue, jue, que, yue], ei, uei [written as wei or ui]), bar some interjections, which are generally analysed as lying outside the normal system of phonology.

The existence of /ʊ/ as a monophthong is more debatable; it only occurs with the velar nasal /ŋ/ as a final. In Pinyin, it is written ong and thus analyses it as a pairing with /o/, making /o/ a monophthong; however, the five-vowel analysis follows Zhuyin (ㄨㄥ) and analyses it as /w/ + /ə/ + /ŋ/ (while still contrasting with ㄥ -eng). The notation /ʊ/ seems to be the preferred IPA allocation, giving yet another monophthong vowel.

Another example of a diphthong-only vowel is the case of /ɛ/, which only occurs in /jɛn/ and /ɥɛn/ (Pinyin ian and üan as in xuan, juan, quan, yuan). However, there is considerable variation in the realisation of this phoneme [æ ~ e].

Cantonese has fairly clear tense-lax distribution for certain monopthongs, which could be construed as producing 'new' vowel phonemes, e.g. /o/ only found in /ou/ and derived from mononphthong /ɔː/, /e/ only found in /ei/ from /ɛː/.


RP's DRESS vowel is [ɛ]. Its FACE diphthong could be analysed as [ei] or [eɪ] (depending on whether the syllable is open or closed and whether the speaker is a HAPPY-tenser), in which case [e] occurs in diphthongs but not alone. Mind you, those diphthongs could instead be regarded as starting at [ɛ].


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