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In page Punjabi language:

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Phonotactically, long vowels /aː, iː, uː/ are treated as doubles of their short vowel counterparts /ə, ɪ, ʊ/ rather than separate phonemes. Hence, diphthongs like ai and au get monophthongised into /eː/ and /oː/, and āi and āu into /ɛː/ and /ɔː/ respectively.[citation needed]