Trap–bath split

The trap–bath split is a vowel split that occurs mainly in the southern and mainstream varieties of English in England (including Received Pronunciation), in the Southern Hemisphere accents of English (Australian English, New Zealand English, South African English), and also to a lesser extent in older Boston English, by which the Early Modern English phoneme /æ/ was lengthened in certain environments and ultimately merged with the long /ɑː/ of father. (Wells 1982: 100–1, 134, 232–33) Similar changes took place in words with ⟨o⟩; see lot–cloth split.

In this context, the lengthened vowel in words such as bath, laugh, grass, chance in accents affected by the split is referred to as a broad A (also, in the UK, long A). Phonetically, the vowel is [ɑː] in Received Pronunciation (RP); in some other accents, including many Australian and all New Zealand accents, it is a fronter vowel ([ɐː] or [aː]), and it may be a rounded [ɒː] in South African English. In accents unaffected by the split, these words usually have the same vowel as words like cat, trap, man, the short A or flat A.

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