Open vowel in the context of "Low back merger"

The cot–caught merger, also known as the LOT–THOUGHT merger or low back merger, is a phonological phenomenon present in some dialects of English where speakers do not distinguish the vowel phonemes in words like cot versus caught. Cot and caught, along with bot and bought, pond and pawned, etc., are examples of minimal pairs that are lost as a result of this sound change; i.e. each of these pairs of words is pronounced the same. The phonemes involved in the cot–caught merger, the low back vowels, are typically represented in the International Phonetic Alphabet as /ɒ/ and /ɔ/ or, for United States English, as /ɑ/ and /ɔ/. The merger is typical of most Indian, Canadian, and Scottish English dialects as well as some Irish and U.S. English dialects.

An additional vowel merger, the father–bother merger, which spread through North America in the eighteenth and nineteenth centuries, has resulted today in a three-way merger in which most Canadian and many U.S. accents have no vowel difference in words like PALM /ɑ/, LOT /ɒ/, and THOUGHT /ɔ/.

The phonology of the open back vowels of the English language has undergone changes both overall and with regional variations, through Old and Middle English to the present. The sounds heard in modern English were significantly influenced by the Great Vowel Shift, as well as more recent developments in some dialects such as the cot–caught merger.

Canadian raising (also sometimes known as English diphthong raising) is an allophonic rule of phonology in many varieties of North American English that changes the pronunciation of diphthongs with open-vowel starting points. Most commonly, the shift affects /aɪ/ or /aʊ/ , or both, when they are pronounced before voiceless consonants (therefore, in words like price and clout, respectively, but not in prize and cloud). In North American English, /aɪ/ and /aʊ/ usually begin in an open vowel [ä~a], but through raising they shift to [ɐ] , [ʌ] or [ə] . Canadian English often has raising in words with both /aɪ/ (height, life, psych, type, etc.) and /aʊ/ (clout, house, south, scout, etc.), while a number of American English varieties (such as Inland North, Western New England, and increasingly more General American accents) have this feature in /aɪ/ but not /aʊ/. It is thought to have originated in Canada in the late 19th century.

In the U.S., aboot [əˈbut], an exaggerated version of the raised pronunciation of about [əˈbʌʊt], is a stereotype of Canadian English.