In Mitch's answer to "What is the difference between a diphthong and a glide?" and its comments it seems more than one of us is at least a bit confused as to how many phonemes a single diphthong represents:

  1. The two vowel sounds in a diphthong combine to make a single phoneme.
  2. A diphthong is a sequence of two phonemes of a certain kind in a certain relationship.
  3. Sometimes the two sounds of a diphthong are considered to be one phoneme, but sometimes they are each considered separate phonemes, depending on context or something else.

So which of these possibilities is true? And if 3. is true, what are the things that make it one or two phonemes?

3 Answers 3

  1. A diphthong is one sound segment created by a smooth transition between two targets within the same syllable. As a phonetic definition, this makes no theoretical claims about which phoneme(s) represent the articulation in the mind of the speaker.

  2. This statement is a bit vague, but is, as far as I can tell, true in some situations; see below.

  3. The number and character of underlying phonemes that a diphthong corresponds to varies by language and which researcher you talk to. Different kinds of evidence for a particular interpretation of field data are evaluated differently by each specialists, and mainstream phonology has yet to produce a theoretical framework that gives one clear answer to this question for each language.

    In English, for example, the diphthong [e͡ɪ] could be represented underlyingly as either the single phoneme /e͡ɪ/ or a sequence of two phonemes /ej/, where /j/ is the same segment that appears in /jɛs/ "yes". The latter analysis is tempting, since it would reduce the size of the phonemic inventory (all possible underlying segments) of English, but would have to explain the phonetic differences between the /j/ in "yes" and the /j/ in "made", which is much more like an [ɪ]. Of course, the addition of a transformation rule would be standard practice when faced with this situation, but we are then left with the basic question of which is simpler (and thus, more likely to be adopted as a strategy by native speakers): fewer phonemes, or fewer rules?

  • 1
    So, how do you determine whether a particular segment is a phoneme or not? How many phonemes can you find in the word "made"?
    – Alex B.
    Commented Dec 14, 2011 at 17:31
  • if you have such a concept (the phoneme) in a phonological theory you subscribe to.
    – Alex B.
    Commented Dec 14, 2011 at 17:43
  • 2
    An excellent question - this has been alluded to before in answers here and here, but the time has probably come for this to be posted as a top-level question, perhaps titled something like "How is phonemic analysis performed?", maybe with "on an undocumented language" at the end.
    – Alek Storm
    Commented Dec 14, 2011 at 17:48
  • I will answer with a brief overview of generative phonology, which I was taught as an undergrad and remains in the mainstream, and which I enthusiastically disagree with. Spoiler alert: there is no theoretical limit to the number of phonemes that the word "made" can be composed of.
    – Alek Storm
    Commented Dec 14, 2011 at 17:52
  • 1
    It sounds like an interesting forthcoming question. Keep in mind that generative phonologists early on become notorious for trying to abolish the phoneme.
    – user483
    Commented Dec 15, 2011 at 1:09

I'd go with no.1 because you can find the following minimal pairs in English (RP):

could - cowed /ʊ/ versus /aʊ/

cheese - cheers /i/ versus /ɪə/

dead-dared /e/ versus /eə/

bell-bail /e/ versus /eɪ/

buy - boy /aɪ/ versus /ɔɪ/ etc.

For a comprehensive list of minimal pairs in English (RP) compiled by John Higgins, see http://myweb.tiscali.co.uk/wordscape/wordlist/index.html

Thus, a single diphthong in English represents one phoneme.

This is traditional phonology, not generative.

Naturally, other analyses have been proposed, too. For example, a diphthong is treated as a vowel plus a semivowel or another vowel (McCarthy 1952). Thus, you end up having a diphthong consisting of two phonemes under those approaches. Peter Roach (2009) mentions that this view was "almost universally accepted by American (and some British) writers from the 1940s to the 1960s, and still pervades contemporary American descriptions" (p. 104). Roger Lass (1984) argues that analyzing a diphthong as a vowel plus a semivowel /j/ or /w/ is a "shaky position" (p. 138). He also convincingly dismisses the approach proposed in SPE (Chomsky and Halle), characterizing it as "seem[ing] close to lunacy" (p. 138). Bruce Hayes (2008) concludes that the "fewer-phonemes-the-better" analysis is not an iron-clad argument and that the segment/sequence problem is still "an unsettled one in phonology" (p. 57).

  • 5
    You've provided the right answer to the wrong question. This data set shows that English diphthongs are phonemically distinct from their monophthongal (or short, or lax) "counterparts" (except for the last pair) - it says nothing about how many segments are stored in an English speaker's mental phonological system.
    – Alek Storm
    Commented Dec 14, 2011 at 16:09
  • I'm afraid I didn't make myself clear enough. The question is poorly phrased since it is based on the wrong assumption that phonematicity of a diphthong might depend on phonematicity of its structural segments. I would like to emphasize that whether parts of a diphthong are phonemes or not in a particular language is irrelevant for determining phonematicity of a diphthong itself.
    – Alex B.
    Commented Dec 14, 2011 at 16:48
  • I welcome answers that clearly illustrate what might be wrong in the question, especially if they include references. (phonematicity is an interesting word by the way. I'd never heard of it before and it gets only 48 Google hits including some for "Phone, MATI CITY".) Commented Dec 14, 2011 at 18:34
  • 1
    I stand corrected, there is another, more usual, term, phonemicity.
    – Alex B.
    Commented Dec 14, 2011 at 19:53
  • 1
    @ Robin, it depends on your dialect. Some pronounce "bell" as [bɛl], some as [bel] (like me).
    – Alex B.
    Commented Jan 3, 2012 at 21:44


Here is what I used the last time I searched for the same thing before this website. Diphthongs are considered one phoneme with two targets, meaning the tongue moves during the pronunciation of the vowel.

  • Interestingly, the Wikipedia article now says, "In some languages, diphthongs are single phonemes, while in others they are analyzed as sequences of two vowels, or of a vowel and a semivowel." Elsewhere it references www-01.sil.org/linguistics/GlossaryOfLinguisticTerms/… to say, "Diphthongs often form when separate vowels are run together in rapid speech during a conversation. However, there are also unitary diphthongs, as in the English examples above, which are heard by listeners as single-vowel sounds (phonemes)." Commented Jun 21, 2016 at 11:07
  • I love Wiki more than anyone, it's so useful, insightful...BUT you should NOT cite wikipedia. Commented Oct 18, 2019 at 0:04

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