Articulatory Phonetics 101: Diphthongs

This is Part 11 of a series covering the basics of articulatory phonetics, the study of how humans physically produce speech sounds. For the full list of posts, see the Articulatory Phonetics 101 Index.

When we last left off, we had just covered the basics of vowel production. We’re almost — almost — done with the basics of articulatory phonetics, but we have one last thing to cover, real quick:

What’s the vowel in “hi”?

If you remember what we discussed in the vowel basics article, you’ll remember that from the articulatory point of view, a vowel is defined by the position of the highest point of the tongue — specifically, how high and how far back it is. What you’ll find, though, is that when you say “hi”, your tongue moves from one position to another, creating a change in the vowel quality. In this case, the vowel begins as /a/, a low central vowel, and ends as /ɪ/, a high front lax vowel. This vowel is a diphthong, a vowel with two (Greek di-) different vowel qualities (Greek phthongos, “tone”).

Phonologically, diphthongs are considered one vowel, rather than two. If we want to indicate for clarity that /haɪ/ contains a diphthong, we can draw a tie bar over it: /ha͡ɪ/. Alternatively, we can write the diacritic ̯ under /ɪ/ to indicate that /ɪ/ is not a syllable: /haɪ̯/. (If you want to be really particular about their use, they can be used to specify slightly different things, but we won’t get into that here.)

If you ever need to indicate that two adjacent vowels are separate syllables instead of a diphthong, you can insert a syllable break . to indicate that the two vowels do not form a diphthong: /a.ɪ/.

Diphthongs of English

Depending on what variety of English you speak, you may have different numbers of diphthongs. General American has five diphthongs, and Received Pronunciation has eight diphthongs.

General American diphthongs:

  • /aɪ/ as in “hi
  • /aʊ/ as in “how
  • /ɔɪ/ as in “boy
  • /eɪ/ as in “hay
  • /oʊ/ as in “hoe” (the gardening implement — minds out of gutters, please)

Received Pronunciation (or the Queen’s English, or BBC English — take your pick) diphthongs:

  • /aɪ/ as in “hi
  • /aʊ/ as in “how
  • /ɔɪ/ as in “boy
  • /eɪ/ as in “hay
  • /əʊ/ as in “hoe” (General American /oʊ/)
  • /ɪə/ as in “here” (General American /ɪɹ/)
  • /ɛə/ as in “hair” (General American /ɛɹ/)
  • /aə/ as in “hire” (General American /aɪɹ/)

/aɪ/, /aʊ/ and /aə/ begin with the low central vowel /a/, which otherwise does not appear in English.

/eɪ/ and /oʊ/ are of particular note here, because in General American and Received Pronunciation, /e/ and /o/ always appear as diphthongs. In broad transcription, it’s up to you whether you want to write out the full diphthongs /eɪ/ and /oʊ/, or if you want to leave them as /e/ and /o/.


That’s all I’ve got for you today. I’ll have a round-up post next week that quickly revisits all the most important concepts in articulatory phonetics, like a cheat sheet. See you all next week!