American English Diphthongs

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English diphthongs

In this little note we will describe the diphthongs found in American English. For the sake of completeness, we will also cover British English diphthongs. A diphthong in the English language is two vowels pronounced one after another with the following characteristics:

  • Both vowels have to be lax (see [Go12a] for the definition of a lax vowel).
  • Of the two vowels, the first one is the most important in terms of stress. This means that, for example, in diphthong [aɪ], sound [a] is much longer and stronger than sound [ɪ]. Furthermore, the intonation pattern is falling.
  • Pronunciation of the vowels take place through a glide, that is, through a continuous, smooth movement from the first vowel to the second. They are not articulated separatedly.

Examples of diphthongs are: [aɪ] as in high[haɪ], [eɪ] as in play[pleɪ], [ɔɪ] as in boy[bɔɪ], or [aʊ] as in now[naʊ].

According where the glide in the diphthong ends, they are classified as closing diphthongs (or rising diphthongs) and centering diphthongs. Closing diphthongs are those whose last vowel is near-high. Since both vowels have to be lax, the only two possibilities are [ɪ] and [ʊ]. Centering diphthongs ends in vowel [ə] (schwa). American English diphthongs can be explained from their British counterpart. Figure 1 illustrates the classification of British English diphthongs. If a diphthong carries is labelled with (BrE) it means that diphthong only occurs in British English; similarly, label (AmE) is used when the diphthong only appears in American English.

Figure 1: Classification of American English diphthongs.


Diphthongs [aɪ], [eɪ], [ɔɪ], and [aʊ] are present in American and British English. However, diphthong [əʊ] is only found in British English. In American English it is always replaced by [oʊ], where vowel [o] is a close mid back short lax rounded sound. Again, this sound only occurs in diphthongs.

Diphthongs [ɪə], [eə], and [ʊə] as such do not occur in American English. The final schwa is substituted by retroflex approximant [ɻ] or rhotic accent; see [Go12b] for further information on rhotic accent.We will indicate the rhotic accent by r in transcription. Therefore, those diphthongs are converted into vowels with rhotic accent [ɪr], [er], and [ʊr]. Technically, they are not diphthongs any more as they are not composed of the gliding of two vowels.

Figure 2 shows more graphically the glides of diphthongs.

Figure 2: Diphthong gliding.

In order to form a diphthong tense vowels are reduced to short lax vowels. Thus in boy the diphthong is not formed with long o-sound [ɔ:] but with its short lax version [ɔ] (tongue and lip position remains the same). Similarly, in high the diphthong is pronounced with vowel [a] instead of vowel [a:]. Vowel [a] is a front low short lax unrounded sound. Both sounds [ɔ] and [a] are only used in diphthongs and never are found as pure vowels.

To finish up this little note here we have a few videos from Rachel's English [RE]


Pronunciation of [oʊ]

Pronunciation of [aʊ]

Pronunciation of [eɪ]

Pronunciation of [ɔɪ]

Pronunciation of [aɪ]

Note: On her web page Rachel states that [ju:] is also a diphthong. We believe that is an incorrect statement. Sound [j] is a semivowel and as such it is considered by most phoneticians; see [Go13], Section 4.6 for a technical explanation.

In the references below the reader can find further information on diphthongs.


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