The Separate Letters that begin some surahs

Preface: The letters that begin some of the surahs of the Qur’an are fourteen in number.  These fourteen letters are found in the phrase:
"" These letters are divided into four groups:

       1.  That which has no medd at all: This refers to the  alif   ()  as it has no medd letter in it.

       2.  That which has a medd of two counts: The letters in this category can be found in the phrase:
"" meaning the letters are recited as when found in the letters that sometimes begin a surah, and are lengthened two counts.  When these letters are written out as above, they consist of only two letters, and are of the natural medd
().

       3.  That which has a medd of six vowel counts: The rest of the letters from the fourteen that start some surahs of the Qur’an fall into this category.  These letters are seven in number, and can be found in the phrase: "".  All are lengthened six counts.   The letters of the group are categorized into to two groups:
 The Light Compulsory Lengthening in a letter and The Heavy Compulsory Lengthening in a letter  .  
The category that the letter falls into depends on whether it is merged into the next letter, or not. 

       4.  The "": The  can be lengthened four or six vowel counts, according to the rules of the way we read, which is the way of: Hafs ‘an ‘Aasim from the way of Shatibiyyah 
( ).   This is due to the fact that the as a separate letter of an opening to a surah is found at the beginning of surah Maryam    click here to listen to this aayah, 
and the beginning (second aayah) of surah Ash-Shooraa .    

The Compulsory Light Lengthening in Letters

Its definition: The letters of the group "" are each individually read as a three letter word, the middle letter being a medd letter, andthe third letter having an original (or permanent) sukoon.  The determiner of the letter being  or  is the last letter and whether it merges with the first letter of the next three letter word or not.  In the case of  the  letter, it is not merged with what comes next.  This is why it is called .  This medd is lengthened six vowel counts.

Examples:  

Click here to listen to this aayah 

In this example we can see that the  when written out consists of three letters; the middle letter is a medd letter (alif) , the last letter
("") has a sukoon it, and is followed by a , which the  does not merge into, and therefore it is called .

The Compulsory Heavy Lengthening in Letters

Its definition: This type of lengthening occurs when a letter of the "" group of letters that begin some of the surahs, (as described above), has the last letter of the three letter word representing the individual letter, merging into the letter that comes after it.  This is the reason for it being called  (heavy). This medd has a required lengthening of six counts.   

Example:   

Click here to listen to this aayah

In this example, we find two letters, the  and the  that consist of three letters. The  has a medd letter as the middle letter, then followed by a letter that is a  sakinah, but merged with the first letter of the next spelled out letter . The  is then .  The  does not have its third letter merging with what comes next (there is none after the meem), so it is .

The different separate letters that are found at the beginning of some surahs appear in the following combinations: