Question
What is the use of haroof yarmaloon how many in number?
Answer
The group of letters that form the word

are six in number. The letters are: The

,

,

,

,

, and the

. They are significant when any of these six letters follow a

saakinah (vowelless) or tanween, the

saakinah or the

saakinh of the tanween merge into these letters, which is called

in Arabic. Please see the following link for full explanation of this rule and the role of the letters in the group

.
http://www.abouttajweed.com/the-noon-saakinah-and-tanween/merging-of-the-noon-saakinah-and-tanween-p-2.html