Some notable exceptions to this monophthongization are some rural Lebanese dialects, which preserve the original pronunciations of some of the diphthongs.
Some varieties might maintain the diphthong for words recently borrowed from Standard Arabic or use them in free variation.
[3] Smoothing is a monophthongization of a closing diphthong (most commonly /eɪ, aɪ, ɔɪ, əʊ, aʊ/) before a vowel that can occur in Received Pronunciation and other accents of English.
Smoothing applies particularly readily to /aɪ/ and /aʊ/ when preceding /ə/, hence [faːə] for fire and [taːə] for tower, or with the syllabicity loss of /ə/, [faə̯, taə̯].
[4] Smoothing can occur across word boundaries in the same conditions (closing diphthong + vowel), as in [weː aʊt] way out, [ðeː iːt] they eat, [ɡəː ɒf] go off.
[6] In Hindustani, the pure vowels /ɛː/ and /ɔː/ are written with the letters for the diphthongs ai and au in Devanagari and related alphabets.
[7] It changed the diphthongs ie [iə], uo [uə] and üe [yə] to respectively ie [iː], u [uː] and ü [yː]: Before 11th century > nowadays: The digraph "ie" has kept its spelling despite monophthongization.