Shiavault - a Vault of Shia Islamic Books A Hundred and One Rules in Arabic Grammar! Long vowel to a Diphthong. ============================== If any of the two long vowel و, ا ** ** is proceeded by the short vowel**–َ** ** **, the long vowel changes its character to a diphthong: uu - ou دَور ، دور ii - ei **دَين ** ** ** ، دين Previous Next