The trap–bath split (also TRAP–BATH split) is a vowel split that occurs mainly in mainstream and southeastern accents of English in England (including Received Pronunciation), in New Zealand English and South African English, and also to a lesser extent in Australian English as well as older Northeastern New England English (notably, older Boston accents), by which the Early Modern English phoneme /æ/ was lengthened in certain environments and ultimately merged with the long /ɑː/ of father. In this context, the lengthened vowel in words such as bath, laugh, grass, chance in accents affected by...