Phonological history of English vowels

Great Vowel Shift and trisyllabic laxing

Tense–lax neutralization

Monophthongs

Low front vowels

• /æ/ tensing is a process that occurs in some accents of North American and some Australian English whereby the vowel is raised and lengthened or diphthongised in various environments. In some dialects it involves an allophonic split whilst in others it affects all s. There are dialects, however, where the split is phonological.
• The bad–lad split is a phonological split of the Early Modern English short vowel phoneme into a short and a long. This split is found in some varieties of English in England and Australia.
• In Modern English, a new phoneme,, developed that did not exist in Middle English.
• The trap–bath split is a vowel split whereby the Early Modern English phoneme merged with the in certain environments. It occurs mainly in southern varieties of English English, the Boston accent and the Southern Hemisphere accents.

  Low back vowels

• The father–bother merger is a merger of the Early Modern English vowels and that occurs in almost all varieties of North American English.
• The lot–cloth split is the result of a late 17th-century sound change that lengthened to before voiceless fricatives, voiced velars and also before in the word gone.
• The cot–caught merger is a phonemic merger that occurs in some varieties of English causing the vowel in words like cot, rock, and doll to be pronounced the same as the vowel in the words caught, talk, law, and small.
• The psalm–sum merger is a phenomenon occurring in Singaporean English where the phonemes and are both pronounced. In Australian English they are distinguished only by vowel length.
• The bud–bird merger is a merger of and occurring for some speakers of Jamaican English.

  High back vowels

• The foot–goose merger is a phonemic merger of the vowels and found in distinct dialects of English: Scotland, Northern Ireland and the far north of England use for both these sets of words.
• The foot–strut split is the split of Middle English into two distinct phonemes and that occurs in most accents of English.
• The strut–comma merger is the merger of and found in Welsh English and in many varieties of General American.
• In Modern English, the vowels,, and of Middle English have been merged.

  High front vowels

• The weak vowel merger is a phonemic merger of the unstressed with with in certain dialects of English. As a result of this merger the words rabbit and abbot rhyme.
• The kit split is a split of EME found in South African English, where kit and bit do not rhyme.
• The pin–pen merger is a conditional phonemic merger of and before the nasal consonants, and.
• Happy tensing is the process in which final lax becomes tense in words like happy.
• The meet–meat merger is the merger of the Early Modern English vowel with the vowel. The merger is complete outside the British Isles and virtually complete within them.
• The mitt–meet merger is a phenomenon occurring in Malaysian English and Singaporean English where the phonemes and are both pronounced.
• The met–mat merger is a phenomenon occurring in Malaysian English and Singaporean English where the phonemes and are both pronounced.
• The met–mate merger is a phenomenon occurring for some speakers of Zulu English where and are both pronounced.
• The thank–think merger is the lowering of to before the velar nasal that can be found in the speech of speakers of African American Vernacular English.
• The pit–pet merger is a complete merger of and – not restricted to positions before nasals – occurring for some speakers of Newfoundland English.

  Schwa

Diphthongs

• The vein–vain merger is the merger of the Middle English diphthongs and that occurs in all dialects of present English.
• The following mergers are grouped together by Wells as the long mid mergers. They occur in all but a few dialects of English.
• *The pane–pain merger is a merger of the long mid monophthong and the diphthong.
• *The toe–tow merger is a merger of the Early Modern English vowels and.
• The cot–coat merger is a phenomenon occurring for some speakers of Zulu English where the phonemes and are not distinguished.
• The rod–ride merger is a merger of and occurring for some speakers of African American Vernacular English and Southern American English.
• The pride–proud merger is a merger of the diphthongs and before voiced consonants occurring for some speakers of African American Vernacular English.
• The rode–road merger is the merger of /oː/ and /oə/ occurring for most English speakers. Some Welsh English speakers distinguish "rode" /roːd/ and "cole" /koːl/ from "road" /roəd/ and "coal" /koəl/.
• The muse–mews merger is the merger of /yː/ and /ɪu/ occurring for most English speakers. Some Welsh English speakers distinguish "muse" /myːz/ and "due" /dyː/ from "mews" /mɪuz/ and "dew" /dɪu/.
• The line–loin merger is a merger between the diphthongs and that occurs in some English dialects.
• The coil–curl merger is a merger of and which historically occurred in some dialects of English. It is particularly associated with the dialects of New York City and New Orleans.

  Vowel changes before historic /r/

Mergers before intervocalic /r/

• The Mary–marry–merry merger is the merger of and with .
• The mirror–nearer merger is the merger of with .
• The hurry–furry merger is the merger of with.
• The furry–ferry merger, common in the Philadelphia accent, is the merger of with.
• Intervocalic merges either with as in starry or as in glory.

  Mergers before historic coda /r/

• The cheer–chair merger is the merger of the Early Modern English sequences and, which is found in some accents of modern English.
• The fern–fir–fur merger is the merger of the Middle English vowels into when historically followed by in the coda of the syllable.
• The fur–fair merger is a merger of with that occurs in some accents.
• The nurse–near merger is a possible merger of with that may occur in some American and the West Country English dialects.
• The –– merger is found in some accents of Southern British English. It causes tire, tower, and tar to be homophones. The – merger is found in some Midland and Southern U.S. accents. It causes tire and tar to be homophones.
• The cure–fir merger is a merger of with or with that occurs in East Anglian and American English in certain words.
• The pour–poor merger is the merger of with.
• The card–cord merger is a merger of Early Modern English with, found in some Caribbean, English West Country and Southern and Western U.S. accents.
• The horse–hoarse merger is the merger of and before historic occurring in most varieties of English.
• The square–nurse merger occurs in some areas of England. The two sets are sometimes merged to and sometimes to .
• The – merger occurs for many speakers of English. It caused power and sour to rhyme.

  Vowel changes before historic /l/

• The salary–celery merger is a conditioned merger of and before occurring in New Zealand and Victorian English.
• The fill–feel merger is a conditioned merger of and before /l/ occurring in some dialects of American English.
• The fell–fail merger is a conditioned merger of and before occurring in some varieties of Southern American English.
• The full–fool merger is a conditioned merger of and before mainly occurring the North Midland accent of American English.
• The hull–hole merger is a conditioned merger of /ʌ/ and /oʊ/ before /l/ occurring for some speakers of English English with l-vocalization.
• The doll–dole merger is a conditioned merger, for some Londoners, of /ɒ/ and /əʊ/ before nonprevocalic /l/.
• The vile–vial merger involves a partial or complete dephonologicalization of schwa after a vowel and before coda.
• Four other conditioned mergers before which require more study have been mentioned in the literature and are as follows:
• * and
• * and
• * and
• * and