Shiavault - a Vault of Shia Islamic Books A Hundred and One Rules in Arabic Grammar! The Sun Letters. =================== Due to a Phonological rule, the / ل / sound of the definite article is assimilated by any of the following sun consonants. Therefore, you need to use Shadda to replace the assimilated / ل /. The Sun Letters are: **ت ث د ذ ر ز س ش ص ض ط ظ ن الدَّرسُ** Previous Next