The Number of Diphthongs in English Language

This text lists three sources (Daniel Jones, J. D. O’Connor and A. C. Gimson) about the English diphthongs in British English/Received Pronunciation.  This is a simplified classification and by no means complete.

The most detailed overview gives Jones (1975), who lists the important and less important diphthongs. The “essential diphthongs” (98) are: ei, ou, ai, au, ɔi, iə, ɛə, ɔə, uə; including “rising” ones: ĭə, ŭə, ŭi. Jones than continues with a note that two of those diphthong can be ignored by foreign speakers: ɔə and ŭi. The diphthong ɔə because it is replaced by ɔ:, and ŭi since “it can always be replaced by disyllabic u-i”. “(…) Nine further  non-essential diphthongs”, according to Jones, are: oi, ui, eə, aə, aə, oə, ŏi, ĕə, ŏə. They can be replaced by their “fuller forms”.

If you need to search for diphthongs in a specific context, take a look at FONRYE program that searches a phonetic dictionary.

Thus Jones gives 10 important diphthongs: ei, ou, ai, au, ɔi, iə, ɛə, uə, ĭə and ŭə. (They are not in slash parentheses; they are left as in the original text).

The next author is J. D. O’Connor (1973), who list 9 diphthongs (153): /eɪ/, /əʊ/, /ɑɪ/, /aʊ/, /ɔɪ/, /ɪə/, /ɛə/, /ɔə/ and /ʊə/. He then continues with the explanation that /ɔ:/ and /ɔə/ are not separated in pronunciation (“relatively few RP speakers make a contrast”) , so /ɔə/ is not essential.

In O’Connor’s division there are 8 essential diphthongs in British English (RP), as shown above.

Gimson (1970) refers to diphthongs as “diphthongal vowel glides” (126), and lists 8 of them (pp. 127 – 144): /eɪ/, /aɪ/, /ɔɪ/, /əʊ/, /ɑʊ/, /ɪə/, /ɛə/ and /ʊə/. Gimson goes at great depths and analyses each of the diphthongs, further explaining their long and short forms, as well as the variants.

Thus, according to Gimson, there are 8 significant diphthongs in RP English.

To see the sources for the above, visit Books & References page. You can also read a discussion about drawing a diphthong by using its formant frequencies (and calculating the Euclidean distance).