Happy tensing is a variation in English pronunciation that occurs in most accents of English, where words like happy are pronounced instead of older [ˈhæpɪ]. Happy tensing is absent from many varieties of British English and, traditionally at least, from Southern American English. Other realizations of this vowel are also possible, such as [e] in Scottish English.
The history of happy tensing is difficult to pin down; the fact that it is uniformly present in South African English, Australian English, and New Zealand English implies that it was present in southern British English already at the beginning of the 19th century. Yet it is not mentioned by descriptive phoneticians until the early 20th century, and even then at first only in American English.
The term "happy tensing" was coined by John C. Wells in his book Accents of English (Cambridge University Press, 1982).
