Back Vowels

Low back

The low back vowel in American English is /ɑ/, as in father. While many speakers of American English make a distinction between /ɔ/ and /ɑ/, as in the pairs collar– caller [kɑlɚ] – [kɔlɚ], cot– caught [kɑt] – [kɔt], Don– dawn [dɑn] – [dɔn], many others do not make this distinction and use /ɑ/ for both. This collapse of /ɑ/ and /ɔ/ is one of the most significant vowel mergers in American English. The areas where this merger dominates include Maine, New Hampshire, Vermont, northern Massachusetts, Western Pennsylvania, Midland territory, and the American West (with the exception of the metropolitan areas of Los Angeles and San Francisco). The areas resistant to this merger are the inland North (US side of the Great Lakes region), and most of the South and the Northeast corridor (Providence to Baltimore). The merger does not apply when the vowel is followed by a tautosyllabic /ɹ̣/; thus, born and barn are always distinct (cf. orange [ɔɹ̣ənʤ] or [ɑɹ̣ənʤ]). Some speakers around southeastern Ohio and northern West Virginia have /ɑ/ and /ɔ/ neutralized before /t/, but not in other contexts. There are also speakers who limit this merger before nasals (e.g. Don and dawn).

Some books suggest that, in some areas, /ɑ/ has two allophones: [ɑ] and [ɒ]. The vowel [ɒ], which is heard mainly on the Eastern seaboard, has slight lip rounding and lies between [ɑ] and [ɔ]; it is not used by all Americans. For those people who use it, the distribution is as follows: [ɑ] occurs in both open syllables (e.g. spa) and syllables closed by a sonorant consonant (e.g. car, prom), and [ɒ] in syllables closed by an obstruent (e.g. hot, posh).