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Phonological history of English diphthongs

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Title: Phonological history of English diphthongs  
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Language: English
Subject: History of the English language, History of English, English phonology, Middle English creole hypothesis, Great Vowel Shift
Collection: English Phonology, History of the English Language, Splits and Mergers in English Phonology
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Phonological history of English diphthongs

English diphthongs have undergone many changes since the Middle English period. Each of the following sound changes involved at least one phoneme which historically was a diphthong. The sound changes discussed here may also have involved a phoneme which was historically or is now a monophthong. For sound changes involving English-language centering diphthongs see English-language vowel changes before historic r.


  • Vein–vain merger 1
  • Diphthongs of Late Middle English 2
  • Great Vowel Shift 3
  • Diphthongization before velar fricatives 4
    • Taut–taught merger 4.1
    • Wait–weight merger 4.2
  • Late sixteenth century 5
  • Late seventeenth century 6
  • Long mid mergers 7
    • Pane–pain merger 7.1
    • Toe–tow merger 7.2
  • Cot–coat merger 8
  • Poet smoothing 9
  • Rod–ride merger 10
  • Scientific smoothing 11
  • Pride–proud merger 12
  • Line–loin merger 13
  • Coil–curl merger 14
  • Mare–mayor merger 15
  • References 16
  • Bibliography 17
  • See also 18

Vein–vain merger

The vein–vain merger is the merger of the Middle English diphthongs /ei/ and /ai/ that occurs in all dialects of present English. The merger was complete by perhaps the fourteenth century.[1][2]

As a result of the merger, vein and vain are now homophones, but in early Middle English they were pronounced differently as /ˈvein/ and /ˈvain/. Similarly day (from Old English dæġ) and way (from Old English weġ) did not rhyme before the merger.[1]

The merged vowel was a diphthong, often transcribed /ɛi/. It later merged (in most dialects) with the /eː/ of words like pane in the pane–pain merger.

Diphthongs of Late Middle English

The English of South-Eastern England in about 1400 had seven diphthongs:[3]

With front endpoint:

  • /æi/ as in nail, day, whey
  • /ɔi/ as in joy, noise, royal, coy
  • /ʊi/ as in boil, destroy, coin, join

With back endpoint:

  • /ɪu/ as in view, new, due, use, lute, suit, adieu
  • /ɛu/ as in few, dew, ewe, shrewd, neuter, beauty
  • /ɑu/ as in cause, law, salt, change, chamber, psalm, half, dance, aunt.
  • /ɔu/ as in low, soul

Typical spellings are as in the examples above. The spelling Cew (where C represents any consonant) is ambiguous between /ɪu/ and /ɛu/, and the spellings oi and oy are ambiguous between /ɔi/ and /ʊi/.[3] The most common words with Cew pronounced /ɛu/ were dew, few, hew, lewd, mew, newt, pewter, sew, shew ("show"), shrew, shrewd and strew.[3] Words in which /ʊi/ was commonly used included boil, coin, destroy, join, moist, point, poison, soil, spoil, Troy, turmoil and voice, although there was significant variation.[3]

Great Vowel Shift

By the mid sixteenth century, the Great Vowel Shift had created two new diphthongs out of what were formerly close long vowels of Middle English. These were /əɪ/ as in tide, and /əʊ/ as in house.[4] At this period, the English of South-Eastern England could thus have had nine diphthongs.

Diphthongization before velar fricatives

In Middle English, the vowels /a/, /ɛ/, and /ɔ/ were diphthongized when followed by /h/, becoming respectively /au/, /ɛi/, and /ɔu/. The phoneme /h/ was realized as [ç] after front vowels and [x] after back vowels. The elimination of these fricatives resulted in the taut–taught merger and the wait–weight merger.

Taut–taught merger

The taut–taught merger is a process that occurs in modern English that causes /x/ to be dropped in words like thought, night, daughter etc.[5][6][7] /nɪxt/ [nɪçt] > /niːt/, later > /naɪt/ "night" by the Great Vowel Shift.

/x/ sometimes became /f/, with shortening of previous vowel.

Inconsistent development of [x] combined with ambiguity of ou (either /ou/ or /uː/ in Early Middle English) produced multiple reflexes of orthographic ough. Compare Modern English through /θruː/, though /ðoʊ/, bough /baʊ/, cough /kɒf/, /kɔf/ or /kɑf/, rough /rʌf/.

Some accents in northern England show slightly different changes, for example, night as /niːt/ (neat) and in the dialectal words owt and nowt (from aught and naught, pronounced like out and nout, meaning anything and nothing). Also, in Northern England, the distinction between wait and weight is often preserved, so those speakers lack the wait–weight merger.

Wait–weight merger

The wait–weight merger is the merger of the Middle English sound sequences /ɛi/ (as in wait) and /ɛix/ (as in weight) that occurs in most dialects of English.[8]

The main exceptions are in northern England, for example in many Yorkshire accents, where these sequences are often kept distinct, so that wait /weːt/ is distinct from weight /wɛɪt/ and late /leːt/ does not rhyme with eight [ɛɪt].

The distinction between wait and weight is an old one that goes back to a diphthongisation of Middle English /ɛ/ before the fricative /x/ which was represented by gh in English. So in words like weight /ɛ/ became /ɛɪ/ and subsequently /x/ was lost as in Standard English, but the diphthong remained.

Wait on the other hand is a Norman French loanword (which in turn was a Germanic loan) and had the Middle English diphthong [ai] that was also found in words like day. This diphthong merged with the reflex of Middle English /aː/ (as in late) and both ended up as /eː/ in the accents of parts of northern England, hence the distinction wait /weːt/ vs. weight /wɛɪt/.

Note that the wait–weight merger is distinct from the pane-pain merger, where the formerly distinct vowels /eː/ and /ei/ have since merged as /eɪ/. Words like ate, ait and eight all had different pronunciations in Middle English, but are homophones in most accents today.

Late sixteenth century

By the end of the sixteenth century, the inventory of diphthongs was reduced as a result of several developments, all of which took place in the mid-to-late sixteenth century:[9]

  • the merger of /ɛu/ with /iʊ/, resulting in dew becoming homophonous with due.
  • the pane–pain merger, by which /aɪ/, having become raised to /ɛɪ/, merged with /ɛː/
  • the monophthonging of /aʊ/ to /ɒː/
  • the monophthonging of /ɔʊ/ to /ɔː/

This left /iu/, /ɔɪ/, /ʊi/, /əɪ/ and /əʊ/ as the diphthongs of South-Eastern England.

Late seventeenth century

By the end of the seventeenth century, the following further developments had taken place in the dialect of South-Eastern England:[9]

  • the toe–tow merger, by which /ɔʊ/, having already been monophthongized to /ɔː/ was raised to /oː/.
  • the /iʊ/ of due/dew changed from a falling to a rising diphthong, the result usually being written /juː/ and often analysed as a glide rather than a true diphthong.
  • the diphthongs /əɪ/ and /əʊ/ widen to /aɪ/ and /aʊ/ respectively
  • the diphthong /ʊi/ merges with /aɪ/. In literature from this period there frequently occur rhymes such as "Mind/join'd" (Congreve), "join/line" (Pope), "child/spoil'd" (Swift), "toils/smiles" (Dryden). The present-day pronunciations with /ɔɪ/ in these words result from regional variants which had always had /ɔɪ/ rather than /ʊi/, perhaps influenced by the spelling.[10]

As a result of these changes, there remained only the three diphthongs /aɪ/, /aʊ/ and /ɔɪ/

Long mid mergers

The earliest stage of Early Modern English had a contrast between the long mid monophthongs /eː, oː/ (as in pane and toe respectively) and the diphthongs /ɛi, ɔu/ (as in pain and tow respectively). In the vast majority of Modern English accents these have been merged, so that the pairs pane/pain and toe/tow are homophones. These mergers are grouped together by Wells[11] as the long mid mergers.

Pane–pain merger

The pane–pain merger is a merger of the long mid monophthong /eː/ and the diphthong /ei/ that occurs in most dialects of English. In the vast majority of Modern English accents the vowels have been merged; whether the outcome is monophthongal or diphthongal depends on the accent. But in a few regional accents, including some in East Anglia, South Wales, and even Newfoundland, the merger has not gone through (at least not completely), so that pairs like pane/pain are distinct.

A distinction, with the pane words pronounced with [eː] and the pain words pronounced with [æɪ], survived in Norfolk English into the 20th century. Trudgill describes the disappearance of this distinction in Norfolk, saying that "This disappearance was being effected by the gradual and variable transfer of lexical items from the set of /eː/ to the set of /æɪ/ as part of dedialectalisation process, the end-point of which will soon be (a few speakers even today maintain a vestigial and variable distinction) the complete merger of the two lexical sets under /æɪ/ — the completion of a slow process of lexical diffusion."[12]

Walters (2001)[13] reports the survival of the distinction in the Welsh English spoken in the Rhondda Valley, with [eː] in the pane words and [ɛi] in the pain words.

In accents that preserve the distinction, the phoneme /ei/ is usually represented by the spellings ai, ay, ei and ey as in day, play, rain, pain, maid, rein, they etc. and the phoneme /eː/ is usually represented by aCe as in pane, plane, lane, late etc. and sometimes by eCe and e as in re, cafe, Santa Fe etc.

Toe–tow merger

The toe–tow merger is a merger of the post-Early Modern English vowels /oː/ (as in toe) and /ou/ (as in tow) that occurs in most dialects of English. (The vowels in Early Modern English itself were /ɔː/ and /ɔu/ respectively, but this changed with the Great Vowel Shift.)

The merger occurs in the vast majority of Modern English accents; whether the outcome is monophthongal or diphthongal depends on the accent. The traditional phonetic transcription for General American and earlier Received Pronunciation in the 20th century is /oʊ/, a diphthong. But in a few regional accents, including some in Northern England, East Anglia and South Wales, the merger has not gone through (at least not completely), so that pairs like toe and tow, moan and mown, groan and grown, sole and soul, throne and thrown are distinct.

In 19th century England, the distinction was still very widespread; the main areas with the merger were in the northern Home Counties and parts of the Midlands.[14]

The distinction is most often preserved in East Anglian accents, especially in Norfolk. Peter Trudgill[12] discusses this distinction, and states that "...until very recently, all Norfolk English speakers consistently and automatically maintained the nose-knows distinction... In the 1940s and 1950s, it was therefore a totally unremarkable feature of Norfolk English shared by all speakers, and therefore of no salience whatsoever."

In a recent investigation into the English of the Fens,[15] young people in west Norfolk were found to be maintaining the distinction, with [ʊu] or [ɤʊ] in the toe set and a fronted [ɐʉ] in the tow set, with the latter but not the former showing the influence of Estuary English.

Walters (2001)[16] reports the survival of the distinction in the Welsh English spoken in the Rhondda Valley, with [oː] in the toe words and [ou] in the tow words.

In accents that preserve the distinction, the phoneme descended from Early Modern English /ɔu/ is usually represented by the spellings ou, and ow as in soul, dough, tow, know, though etc. or through L-vocalization as in bolt, cold, folk, roll etc., while that descended from Early Modern English /ɔː/ is usually represented by oa, oe, or oCe as in boat, road, toe, doe, home, hose, go, tone etc.

Cot–coat merger

The cot–coat merger is phenomenon occurring for some speakers of Zulu English where the phonemes /ɒ/ and /oʊ/ are not distinguished making "cot" and "coat" homophones. Zulu English also generally has a merger of /ɒ/ and /ɔː/, so that sets like "cot", "caught" and "coat" can be homophones.[17]

Poet smoothing

Poet smoothing is a process occurring in many varieties of British English where bisyllabic /əʊ.ə/ is pronounced as the diphthong [ɜɪ] in many words. In these varieties, "poet" is pronounced as monosyllabic [ˈpɜɪt] and "poem" is pronounced [ˈpɜɪm].

Rod–ride merger

The rod–ride merger is a merger of /ɑ/ and /aɪ/ occurring for some speakers of African American Vernacular English (AAVE), in which rod and ride are merged as /rad/. Some other speakers of AAVE may keep the contrast, so that rod is /rɑd/ and ride is /raːd/.[18]

Scientific smoothing

Scientific smoothing is a process that occurs in many varieties of British English where bisyllabic /aɪ.ə/ becomes the triphthong /aɪə/ in certain words with /aɪ.ə/. As a result, "scientific" is pronounced /saɪən.ˈtɪf.ɪk/ with three syllables and "science" is pronounced /ˈsaɪəns/ with one syllable.[19]

Pride–proud merger

The pride–proud merger is a merger of the diphthongs /aɪ/ and /aʊ/ before voiced consonants into monophthongal /ä/ occurring for some speakers of African American Vernacular English making pride and proud, dine and down, find and found etc. homophones. Some speakers with this merger, may also have the rod–ride merger hence having a three–way merger of /ɑː/, /aɪ/ and /aʊ/ before voiced consonants, making pride, prod, and proud and find, found and fond homophones.[18]

Line–loin merger

The line–loin merger is a merger between the diphthongs /aɪ/ and /ɔɪ/ that occurs in some accents of Southern English English, Hiberno-English, Newfoundland English, and Caribbean English. Pairs like line/loin, bile/boil, imply/employ are homophones in merging accents.[20]

Coil–curl merger

The coil–curl merger is a vowel merger, now moribund, which historically occurred in some dialects of English. It is particularly associated with the early twentieth-century dialects of New York and New Orleans.

The merger caused the vowel classes associated with the General American phonemes /ɔɪ/, as in choice, and /ɝ/, as in nurse, to merge, making coil and curl homophones. The merged vowel was typically a diphthong [ɜɪ], with a mid-central starting point, rather than the back rounded starting point of /ɔɪ/ in most other accents of English. The merger happened only before a consonant; stir and boy never rhymed.[21]

The merger is responsible for the "Brooklynese" stereotypes of bird sounding like "boid" and thirty-third sounding like "toity-toid". The songwriter Sam M. Lewis, a native New Yorker, rhymed returning with joining in the lyrics of the English-language version of "Gloomy Sunday".

According to a survey that was done by William Labov[22] in New York in 1966, 100% of the people over 60 used [ɜɪ] for bird. With each younger age group, however, the percentage got progressively lower: 59% of 50–59-year-olds, 33% of 40–49-year-olds, 24% of 20–39-year-olds, and finally, only 4% of people 8–19 years old used [ɜɪ]. Nearly all native New Yorkers born since 1950, even those whose speech is otherwise non-rhotic, now pronounce bird as [ˈbɝd].

Mare–mayor merger

The mare–mayor merger is a process occurring in many varieties of British English, as well as the Philadelphia dialect and Baltimorese, where bisyllabic /eɪ.ə/ is pronounced as the central diphthong /eə/ in many words. In these varieties, "mayor" is pronounced /ˈmeə/, homophonous with "mare".

In North American English accents with the merger, it also affects sequences without /r/, where some words with the /eɪ.ə/ sequence merge with /eə/ associated with æ-tensing. Because this particular /eə/ derived from /æ/, such words are frequently hypercorrected with /æ/. The best known examples of this are mayonnaise (/ˈmeəneɪz~ˈmæneɪz/) and graham (/ˈɡreəm~ˈɡræm/, a homophone of gram).


  1. ^ a b  
  2. ^ Index.html
  3. ^ a b c d Barber, pp. 112-116
  4. ^ Barber, p. 108
  5. ^
  6. ^ *
  7. ^ [1]
  8. ^ (Wells 1982: 192–94, 337, 357, 384–85, 498)
  9. ^ a b Barber, pp. 108, 116
  10. ^ Barber, pp. 115-116
  11. ^ Wells, ibid., 192–94, 337, 357, 384–85, 498
  12. ^ a b Norfolk England Dialect Orthography
  13. ^ Walters, J. R. (2001). "English in Wales and a 'Welsh Valleys' accent". World English 20: 283–304. 
  14. ^ Britain, D. (2001). "Where did it all start? Dialect contact, the 'Founder Principle' and the so-called (-own) split in New Zealand English". Transactions of the Philological Society 99: 1–27.  
  15. ^ Britain, D. (2002). "Surviving 'Estuary English': Innovation diffusion, koineisation and local dialect differentiation in the English Fenland" (PDF). Essex Research Reports in Linguistics 41: 74–103. 
  16. ^ Walters, ibid.
  17. ^ Rodrik Wade, MA Thesis, Ch 4: Structural characteristics of Zulu English at the Wayback Machine (archived May 17, 2008)
  18. ^ a b Wells, ibid., 557
  19. ^ Wells, John "Whatever happened to received pronunciation?" Wells: Whatever happened to received pronunciation? Author's webpage; accessed 19 April 2011.
  20. ^ Wells, ibid., 208–10
  21. ^ Wells, ibid., 508 ff.
  22. ^  


  • Barber, Charles Laurence (1997). Early modern English (second ed.). Edinburgh: Edinburgh University Press.  

See also

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