Identical consecutive letters
Shadda (ــّـ)
When an unvowelled letter is followed by itself (but vowelled) in the same word, it is written only once and a tiny w-like sign ــّـ is placed above it. The vowel of the second letter is placed above/below the w-like sign (details below). Though it is written only once, the letter is pronounced twice, once together with the preceding letter and the second time as a vowelled letter, like in:
مَدَّ : mad-da
كُلُّ : kul-lu
Note:
This rule of contracting the identical letters into one does not apply when the definite article is followed by a word starting with ل.
This rule of contracting the identical letters into one does not apply when the definite article is followed by a word starting with ل.
The vowel of the second letter is placed on the ــّـ if it is a ــَـ or ــُـ. If it is a ــِـ it is placed either below the ــّـ or below the letter itself. The second letter must carry a single or a double vowel; it cannot have a ــْـ.