For example, ɔ and ɪ in one word one after another. Note that I talking about a situation where the symbols could be combined as written l, not the sounds. IPA does not have explicit different written display between two monophthongs and one diphthong- a bad symbol choice if any languages have a double vowel sound.

Don't include sentences; refer to words with two vowel sounds.

There are certainly some double consecutive vowel sounds such as continuum.

I ask because I thought about using IPA symbols and whether an ESL learner or even a native could know for sure that two consecutive vowel symbols are really the diphthong assuming no syllable break. continuum has a syllable break between the vowel sounds. I wish to not make this a complaint about IPA.

I teach English and have a TEFL certificate. I wish to limit to basic IPA symbols as shown in Advanced Learner Dictionaries and only General American and Standard British English- that is just about only types of English that most ESL learners ever learn. They have syllable marks and accents- no other diacritics.

  • 1
    I feel like you are defining your question away via excluding 'continuum'. If there's no syllable break, then you're saying it's a diphthong. 'cooperate', 'naive'
    – Mitch
    Feb 19 '17 at 17:49
  • It is not simply NOT TRUE that “IPA does not have explicit different written display between two monophthongs and one diphthong” as you have written. Do please see my revised answer for SIX different ways of doing in IPA this thing that you have written that IPA does not do. It does, and can. Use whichever of those you like best.
    – tchrist
    Feb 19 '17 at 21:46
  • 1
    Could you please clarify your point regarding continuum? Where do you see an ambiguity here? Probably the simplest phonemic representation would be /kənˈtɪnjuəm/, or perhaps /kənˈtɪn·ju·əm/ using middle dots for explicit syllable boundaries in this four-syllable word. Phonetically this could really be written any number of ways depending on the accent and surrounding phonological environment, and which features the transcriber wishes highlighted. One way would be [kʰə̃nˈtʰɪ̃n·juu̯·ə̃m] or [kʰn̩ˈtʰɪ̃·ɲuw·m̩] — which are meant to be the same sounds. (cont.)
    – tchrist
    Feb 19 '17 at 23:43
  • 4
    I'm voting to close this question as off-topic because it is not about English language and usage, but about IPA. It might belong on linguistics.stackexchange.
    – Colin Fine
    Feb 20 '17 at 0:18
  • 1
    @ColinFine I agree. It is only tangentially a situation about English and would make a fine question on linguistics.
    – Mitch
    Feb 20 '17 at 0:44

IPA does not have explicit different written display between two monophthongs and one diphthong — a bad symbol choice if any languages have a double vowel sound.

This statement is untrue, and therefore the conclusion following the dash is unjustified.

I’m going to front-load the solution here before explaining its parts. The bottom line is that you have at least six possible ways in IPA of distinguishing adjacent monophthongs that therefore fall into distinct syllables from a diphthong of the same vowels:

  1. Use an inverted breve diacritic (meaning “non-syllabic”) beneath the IPA symbol for the vowel that is acting as a semi-vowel instead of a full one for the three phonemic diphthongs in English: ⟨aʊ̯⟩ from mouth, ⟨aɪ̯⟩ from price, and ⟨oɪ̯⟩ from choice.

    You can also use those for non-phonemic diphthongs like ⟨eɪ̯⟩ from face, ⟨ou̯⟩ from goat, ⟨ɪi̯⟩ from see, ⟨ʉu̯⟩ from goose, ⟨ʌi̯⟩ from tight, and ⟨eə̯⟩ from tan. However, these are not phonemic, and in many dialects they become monophthongs or different diphthongs than the ones I’ve shown here. For example: “In Scottish, Upper Midwestern, and California English, /eɪ̯/ and /oʊ̯/ are monophthongal [eː] and [oː].” For that matter, even the phonemic diphthongs can be realized as phonetic monophthongs in some dialects: “In several American dialects such as Southern American English, /aɪ̯/ becomes monophthongal [aː] except before voiceless consonants.”

    You should probably avoid confusing learners with highly variable and fairly complicated phonetics, concentrating on phonemics alone, the way Kenyon and Knott do further below.

  2. Use an inverted breve over both vowels to show that they make up just one syllable, so ⟨a͡ʊ⟩ for mouth, ⟨a͡ɪ⟩ for price, and ⟨o͡ɪ⟩ from choice.

  3. Use a superscript for the semi-vowel, so ⟨aᶷ⟩ for mouth, ⟨aᶦ⟩ for price, and ⟨oᶦ⟩ from choice. You could also write those as semi-consonant superscripts, so ⟨aʷ⟩ for mouth, ⟨aʲ⟩ for price, and ⟨oʲ⟩ from choice.

  4. Write the semi-vowel component as the corresponding semi-consonant, as in so ⟨aw⟩ for mouth, ⟨aj⟩ for price, and ⟨oj⟩ from choice for the three phonemic diphthongs. Kenyon and Knott replace ⟨j⟩ with ⟨y⟩ for those last three because that letter is more apt to make native speakers think of the right sound than the [j], which is never spelled that way in native words.

    In Spanish phonology, this strategy of rewriting semi-vowels as semi-consonants is observed only for rising diphthongs, not for falling diphthongs, because in Spanish any adjacent monophthongs that could theoretically fuse to become diphthongs mandatorily do so in all cases, unlike in English.
    Spanish diphthongs
    As you see they just use the semi-consonants as needed for the rising diphthongs, much like Kenyon and Knott do for the falling ones as well.

  5. If you won’t do any of those, then you can also separate adjacent monophthongs with a centered or baseline dot like /ko·ɪnˈsaɪd/ if there is no stress marker between them the way there is in /koˈɪnsɪdəns/.

  6. At last recourse, you can even put a space between adjacent monophthongs, so /ko ɪnˈsaɪd/.

So it is simply not true that you cannot use IPA for languages with consecutive monophthongs. You certainly can: you just need to distinguish that case from the diphthong case, and IPA provides you with many ways of doing that.

IPA even lets you represent the hiatus that occurs in the eel using a glottal stop, /ðiʔ ˈil/. Now even if you do not notice the space, you’ll realize that you stop the glottis there.


IPA does indeed explicitly differentiate the written display of diphthongs. From Wikipedia’s IPA article:


Diphthongs are typically specified with a non-syllabic diacritic, as in ⟨uɪ̯⟩ or ⟨u̯ɪ⟩, or with a superscript for the on- or off-glide, as in ⟨uᶦ⟩ or ⟨ᵘɪ⟩. Sometimes a tie bar is used, especially if it is difficult to tell if the diphthong is characterized by an on-glide, an off-glide, or is variable: ⟨u͡ɪ⟩.


⟨a⟩ officially represents a front vowel, but there is little distinction between front and central open vowels, and ⟨a⟩ is frequently used for an open central vowel. However, if disambiguation is required, the retraction diacritic or the centralized diacritic may be added to indicate an open central vowel, as in ⟨a̠⟩ or ⟨ä⟩.

In the English section of the Wikipedia article on diphthongs, we see more examples of using the special “non-syllabic” diacritic,⟨ ̯ ⟩ (whose code point is U+032F COMBINING INVERTED BREVE BELOW) to show diphthongs in English:


In words coming from Middle English, most cases of the Modern English diphthongs [aɪ̯, oʊ̯, eɪ̯, aʊ̯] originate from the Middle English long monophthongs [iː, ɔː, aː, uː] through the Great Vowel Shift, although some cases of [oʊ̯, eɪ̯] originate from the Middle English diphthongs [ɔu̯, aɪ̯].

Wikipedia chart with English diphthongs

Notice how all those use the inverted breve to show a non-syllabic semi-vowel, the off-glide at the end of a falling diphthong.

I am leaving the rest of this here because I believe it will be useful to future visitors to our site.

This depends in part on how broad or loose the transcription used is, and whether the dot is ever used to represent a syllabic boundary as in [ɔ.ɪ] or with a special diacritic for a non-syllabic vowel like in [oɪ̯]. Here I am using a careful, narrow phonetic representation of actual sounds using square brackets.

These are not phonemic transcriptions, however, and therefore would probably just confuse learners: learners need to train their brains to think about English phonemics the way native speakers do.

Phonemic Systems

There are certain broad phonemic systems where something like coincide might be represented as somewhat close to how coin-side might be represented. It all depends how careful the system’s designer was.

However, systems like that tend to represent the phonemic diphthong in coin using symbols that are different from those used for those two phonemes when they are separate monophthongs. Here’s an example of such a system courtesy of Professor Lawler:

Lawler's phonemic page

In the referenced phonemic system shown in that document originally from Kenyon and Knott as transmitted by Professor Lawler, they use /ay/, /aw/, and /oy/ for English’s three phonemic diphthongs. That uses the /y/ for IPA [j] because there is no need for IPA [y] when representing English phonemes. It also retains the look of the regular, more familiar alphabet, which is of some help here.

Comparing coincide with coin-side

Let’s think about the pair of somewhat similar sounding words coincide and coin-side. Would a learner confuse the adjacent monophthongs of coincide with the phonemic diphthong of coin-side? They shouldn’t, as under the phonemic system just presented, those two would work out to this:

  • coincide /koɪnˈsayd/
  • coin-side /ˈkoynsayd/

Those are pretty obviously not the same thing, so these are not at risk for confusion using phonemics.

But about if we were using phonetics, though, instead of phonemics? Could there now be a problem?

The answer to that here as before again depends on how careful your phonetics are, but if you do it right, there should still be no risk of confusion. A narrow phonetic transcription might run more like:

  • coincide [ˌkʰoʷᵻnˈsäɪ̯d]
  • coin-side [ˈkʰoɪ̯̃ŋsäɪ̯d]

which again are reasonably distinct. They’re also a bear to key in, which is yet another reason why we don’t use narrow phonetics that often.

I recommend use a broad phonemic transcription such as this one when teaching English pronunciation. It does a good job of focusing on what the English-speaking brain focuses on, and of disregarding the narrow phonetic variations seen in the many dozens of allophones.

Phonetic Systems

For the remainder of this post, I will use narrow phonetic transcriptions between square brackets instead of broad phonemic transcriptions between slashes.

I don’t believe the sort of thing you’re talking about ever happens across word boundaries in English. The first of these will never become the second:

  • The saw is all right.  [ðəˈsɔ.ᵻz.ɔɫˈɻäɪ̯ʔ]
  • The soy’s all right.    [ðə ˈsoɪ̯z.ɔɫˈɻäɪ̯ʔ]

Connected speech can be hard to represent for a variety of reasons, but I don’t believe that bisyllabic [ɔ.ɪ] with two monophthongs in hiatus across two syllables can ever fuse into the tautosyllabic diphthong [oɪ̯] in just one. I suppose it may happen in dialects I’m not familiar with.

“Naïve koalas never coöperate with extraördinary knives”

I’m assuming you only care about the three phonemic diphthongs, which are all falling diphthongs. If not, then sometimes you can get one of the two vowels reducing to a glide and producing a rising diphthong, at the cost of that hiatus and therefore of a syllable.

  • koala [kʰoˈɑlə] > [kʰʉˈwɑlə] > [ˈkʰwɑlə] > [ˈkʰʷɑlə]
  • cooperate [kʰoʷˈɑpəˌɻeʲt] > [kʰʉˈwɑpəˌɻeʲt] > [ˈkʰʷɑpɻʷëʔ]

Continuity Hypothesis

In the case of your word continuum, there is a [w] glide there blocking fusion but it may not be written in all transcriptions.

  • Phonemic: /kənˈtɪnjuəm/ or more explicitly /kənˈtɪn·ju·əm/
  • Phonetic:    [kʰə̃nˈtʰɪ̃n·juu̯·ə̃m] or [kʰn̩ˈtʰɪ̃·ɲuw·m̩]

There’s already a phonetic triphthong in the ⟨njuu̯⟩ syllable to the following ⟨ə̃m⟩. I don’t know any argument that could be made in which fusing those would ever be possible, let alone that doing so could produce a tautosyllabic phonetic tetraphthong or pentaphthong or whatever the heck that would make it. I don’t know any way to merge that into the syllabic consonant at the end.

That’s the same reason why naïves [näɪ̯ˈjivz] can never become knives [näɪ̯vz], because here a [j] glide gets in the way.

So often either a [j] or a [w] glide blocks any possibility of fusion, providing a semi-consonantal pivot-point between two syllables. Unlike in the narrow phonetic transcriptions I’m using here, these little glides are seldom written in broad phonemic transcriptions because native speakers always apply them anyway.

In a few other cases, one of the adjacent monophthongs will simply be dropped, the way we also hear in extraordinary [ɛkˈst͡ʂɻʷo˞dəˌneɻi] , where there is no longer an [ə] syllable at the end of extra before starting on the [o] of ordinary the way you would expect if it had been written extra-orginary or extraördinary.


The possible IPA diphthongs in English that I can think of are aɪ aʊ ɔɪ eɪ oʊ, and perhaps eə ɪə ʊə.

Usually, the first element of the diphthong is not possible as an independent vowel phoneme that can precede another vowel phoneme, so there is no ambiguity in principle. The main cases where this is not so clear are aɪ aʊ ɔɪ, and in certain more traditional British transcriptions ɪə ʊə. Usually, the first vowel of the "mouth" and "price" diphthongs is transcribed with /a/, and the "cat" and "father" monophthongs are transcribed with two different vowel symbols, /æ/ and /ɑ/ respectively. But some simplified schemes may collapse together two of these and create some ambiguity. (I don't remember now, but I think I recall hearing of some scheme that uses /ɑɪ/ for "price").

I think confusion is most likely to occur between the diphthong of "choice", and a sequence of separate "aw" and "ih" vowels. A near minimal pair is "boing" and "pawing". But it really depends on the scheme one uses. There are several IPA-based schemes for transcribing English that are currently in common use (in addition to non-IPA based systems like the "binary system" described in the Atlas of North American English (which represents "law" as /loh/, or partially IPA-based sytems like the version of Kenyon and Knott mentioned by tchrist's answer).

John Wells describes some of them on the following web page: IPA transcription systems for English

"Boing" vs. "Pawing" in transcription of British English

Note that the most influential tradition in Britain has been the Gimson "quantitative-qualitative transcription", which makes use of the length marker /ː/ as well as different vowel symbols to indicate the difference between phonologically "short" and "long" monophthongal vowels.

If the length marker is used consistently, there is no risk of confusion even without syllable separators because "boing" is /bɔɪŋ/ while "pawing" is /pɔːɪŋ/. In addition, in many modern British accents /ɔː/ tends to be separated from a following vowel by an epenthetic /r/. If this is taken as phonemic and transcribed, we would have even more differentiation: /bɔɪŋ/ vs. /pɔːrɪŋ/.

"Boing" vs. "Pawing" in transcription of North American English

In transcriptions of North American English, it is less common to use length markers. R-epenthesis is also not present in standard North American varieties. So it seems to me possible that an ambiguous transcription that doesn't differentiate /bɔɪŋ/ and /pɔɪŋ/ might occur in some North American sources. However, depending on the variety, it may make sense to avoid this by writing the "choice" diphthong as /oɪ/ instead of /ɔɪ/. The vowel American speakers use in "law" is generally more open than the vowel used by British speakers; one way of representing this (although I don't see it that often) is to use the symbol /ɒ/, which would allow marking the distinction as /bɔɪŋ/ vs. /pɒɪŋ/. In addition, there are speakers who have the "cot-caught merger" and have replaced the "law" phoneme with /ɑ/ everywhere except before "r". These would have /bɔɪŋ/ (or /boɪŋ/) vs. /pɑɪŋ/.

Centering diphthongs /ɪə/ and /ʊə/ in conservative British English

For /ɪə ʊə/, the situation is somewhat complicated. When stressed, these must be diphthongs because the stressed monophthongs /ɪ/ and /ʊ/ only occur before consonants, not before other vowels. However, in certain traditional British accents, unstressed /ɪ/ and /ʊ/ can be followed by vowels, in words like "marrying" /ˈmærɪɪŋ/ or "actual" /æktʃʊəl/.

I don't speak an accent with these diphthongs, so I don't know to what extent there is any clear distinction between /ɪə̯/ /ʊə̯/ and /ɪ.ə/ /ʊ.ə/ in unstressed syllables. My impression is that the disyllabic sequences /ɪ.ə/ /ʊ.ə/ can often, but probably not always be converted to monosyllabic diphthongs by the process of "smoothing". But as far as I know, smoothing is not mandatory (at least not in all words), so I would think there is still some distinction even in the most conservative accents between the endings of "myriad" (which the OED gives as /ˈmɪrɪəd/) and "bluebeard" (which the OED gives as /ˈbluːbɪəd/): "myriad" is three syllables, or at least can be, while "bluebeard" must be two syllables.

In contemporary British English, a number of speakers have /i/ rather than /ɪ/ in words with the "happy" vowel, and also it is common to replace the centering diphthong /ɪə̯/ with a long monophthong /ɪː/ (It has been common for even longer to replace /ʊə̯/ with /ɔː/.)

So contemporary British English "myriad" and "Bluebeard" could probably be differentiated as /ˈmɪriəd/ and /ˈbluːbɪːd/.

(For more detailed information on the differences between conservative British English pronunciation and contemporary usual pronunciation, see this blog post by Geoff Lindsey: The British English vowel system)

  • I would write boing as [boɪ̯ŋ] since for me it does not have the [ɔ] vowel of paw but the [o] vowel of pore. I think that pawing for me is [ˈpʰɔɪŋ], but I’d be willing to entertain the notion that it might really be [ˈpʰɔʷɪŋ] with a little glide between the two syllables. But if we’re going to use slashes to mean the word’s phonemes not its phonetics, then it doesn’t much matter what we write since those would now be abstract phonemes not concrete sounds, and their realization would vary wildly across the anglosphere. In which case all we need is agreement on shared notation.
    – tchrist
    Feb 19 '17 at 18:10
  • The reason you rarely see /ɒ/ in phonemic transcriptions of North American English is because /ɒ/ is not a phoneme here, even if [ɒ] may occur in some speakers as an allophone of /ɔ/ or /ɑ/. If /ɒ/ were a distinct phoneme, you would be able to prove this using three minimal pairs: an /ɑ,ɒ/ pair, an /ɒ,ɔ/ pair, and an /ɑ,ɔ/ pair. I’ve asked about this before when I asked for a minimal triple for /ɑ,ɒ,ɔ/. I believe the reason none can be shown is because there is no /ɒ/ phoneme here, only at most an [ɒ] allophone, which of course does not count.
    – tchrist
    Feb 19 '17 at 18:38
  • @tchrist: I meant it could just be an alternative representation of the same phoneme as /ɔ/.
    – herisson
    Feb 19 '17 at 18:39
  • 1
    I now think he believes that IPA “cannot” distinguish adjacent monophthongs in two syllables from a diphthong in one. I’m not sure why he thinks this, since it is so far from the truth, but perhaps he’s gotten himself on the “simplified phonemic” notation where these distinctions are casually effaced that gets used by almost all but the most specialist dictionaries.
    – tchrist
    Feb 19 '17 at 21:56

Consider the word drawing. In the Cambridge Dictionary, the transcription for American English is /ˈdrɔ·ɪŋ/. Without the syllable separation dot, you would have the symbol for the diphthong /ɔɪ/. (The British English transcription has the long vowel symbol /ˈdrɔː.ɪŋ/, which means you don't actually need the syllable separation dot.)

And in BrE, it's sometimes pronounced with an intrusive /r/ separating the syllables: /ˈdrɔːrɪŋ/.

The Collins dictionary doesn't use the syllable separation dot, and their AmE phonetic notation for drawing is /ˈdrɔɪŋ/, which is ambiguous. You can tell they mean /ˈdrɔ.ɪŋ/ by looking at the American phonetic notation they use: coin is /koin/ and drawing is /drôˈiŋ/.

The Merriam-Webster phonetic notation for drawing is \ˈdrȯ(-)iŋ\ . What the parentheses mean is: either \ˈdrȯ-iŋ\ or \ˈdrȯiŋ\ . That is, sometimes it is pronounced with two separate vowels /ɔ·ɪ/ and sometimes with the diphthong /ɔɪ/. (I believe some Americans have different pronunciations for the noun /ˈdrɔɪŋ/ and the verb /ˈdrɔ·ɪŋ/.)

  • I suppose that in some accents, drawing might have the same vowel as boing, but it can’t in mine, since for me boing has [oɪ̯] with an [o] not an [ɔ] like drawing has.
    – tchrist
    Feb 19 '17 at 18:02
  • Merriam-Webster and Oxford both seem to indicate that drawing can rhyme with boing in some dialects of AmE. It's not the way I pronounce it, either. Feb 19 '17 at 18:08

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