In many parts of North America (about half the United States and all of Canada) /ɑː/ and /ɔː/ sound the same. This is in addition to the father - bother merger, where /ɑː/ and /ɒ/ sound the same. This means that caught /ɔː/, cot /ɒ/, father /ɑː/ and bother /ɒ/ have all the same stressed vowel /ɑː/. In this accent /ɔː/ appears only followed by /r/: north, force.
This accent is so prevalent that it is used in Merriam Webster Learner's Dictionary and in Cambridge Dictionaries Online for British English, US label. Note that Cambridge Dictionaries Online list two different American pronunciations, and only the one that is labeled US has the cot-caught merger.
Other names for this merger (better for those who have it) are "LOT - THOUGHT merger" or "PALM - LOT - THOUGHT merger". There is an area in the United States (in New England) where "lot" and "thought" are merged as [ɒ] but "palm"/"father" is different (as [ɑ]). This means that strictly speaking "LOT - THOUGHT merger" and "PALM - LOT - THOUGHT merger" are different concepts.
|Sample word||Merriam Webster's
British English - US
|Most American Dictionaries
(if they use IPA)
|cloth||/ɑː/||/ɑː/||/ɔ/||/ɔ/||/ɒ*/ or /ɒBrE, ɔːAmE/|
|force||/oɚ/||/ɔːr/||/ɔr, oʊr/||/ɔr/ and sometimes /oʊr/||/ɔːr/|
|glory||/or/||/ɔːr/||/ɔr, oʊr/||/ɔr/ and sometimes /oʊr/||/ɔːr/|
Sometimes we mark the CLOTH vowel with an asterisk, as follows:
- *: These words are pronounced with /ɔː/ in General American.
The cot-caught merger generates very few homophones.
- bot (computer program; shortening of robot) - bought; collar - caller; cot - caught; don (put clothes on)/Don (nickname of Donald) - dawn/Dawn; stock - stalk;
- William Labov,The Organization of Dialect Diversity in North America, The o/oh merger [i.e. The /ɑː - ɔː/ merger].