This occurs when a word contains a
dipthong, and the reader chooses to stop on
it (whether in the middle or end of an ayah), therefore placing a sukoon
() on the
last letter
Requirement :
Madd letter
Followed by a sukoon (and the reader has chosen to stop on it)
Although this will not be actually visible in the Qur'an, but
is implied as the reader has chosen to stop on it.
The obligatory (laazim) madd that is present in a letter (harfee)
This occurs in some of the letters that are present at the beginning of certain surahs
These surahs begin with some independent letters from the
Arabic alphabet, which are attached to each other like ordinary
words. The individual letters have to be pronounced by reading
out their respective names.
E.g.
The length of each letters' prolongation will be determined
by the Madd rule inherent within the spelling of it
The difference of the length of its prolongation is
determined by the number of letters that are used to spell the
name of that particular letter
So these madd can contain either
three, two or
one letter