Velarization (Heaviness) and Lightness (Part1) 
The definition of tafkheem: Fattening
Its applied definition: It
is a heaviness that enters the body of the letter, so that the mouth is filled
with its reverberation (echo). The method of making a letter have the
characteristic of tafkheem is: elevating the posterior tongue to the roof of
the mouth (soft palate), creating more space between the roof of the mouth and
the bottom of the mouth, and focusing the pressure of the letter to the roof of
the mouth.
The linguistic definition of tarqeeq : Thinness
Its applied definition: It
is a thinness that enters the body of the letter, so the mouth is not filled
with its reverberation (echo).
The Arabic letters are divided into three groups as to tafkheem and tarqeeq:
1. Letters that always
have tafkheem. These are the seven letters in the group 
. They are also called the tafkheem
letters.
2. Letters that have tafkheem sometimes and tarqeeq other times.
a) The lengthened alif.
b) The 
in the
Glorious name of 
.
c) The 
3. Letters that always have tarqeeq. This group consists of the rest of the Arabic alphabet.
The Letters That Always Have Tafkheem
The seven letters of 
group
make up this category. The letters of 
are
. These letters do not all have the
same degree if tafkheem, instead there are differences according to the letter’s
characteristics, and the strength or weakness of these characteristics. Every
time a letter has a strong characteristic, its tafkheem is stronger. 
letters 
) ) are stronger in tafkheem than the rest
of letters
due to the adhesion of the tongue to the roof of the mouth in conjunction with
the elevation of the tongue. The ranking of letters
from strongest is 
then 
, then 
, then 
, then 
, then 
, then 
.
Levels of Tafkheem
There are two different schools of thought when it comes to tafkheem. Both are correct, but the reader should follow one or the other in their reading.
Three Levels of Tafkheem
This school of thought has three
different levels in tafkheem. The strongest being the tafkheem letter that has
a fat-h, the second being the tafkheem letter with a dhammah, and the third
level, the tafkheem letter with a kasrah. The saakin tafkheem letter follows
the level of tafkheem of the vowel on the letter before it. This means if the
tafkheem letter is saakin, and the letter before it has a fat-ha, then the
tafkheem letter will be at the highest level of tafkheem (as the in: 
) . The
saakin letter of tafkheem preceded by a dhammah would have the second level of
tafkheem (as the in : 
. The
saakin tafkheem letter preceded by a kasrah is at the lowest level of tafkheem
(such as the in : 
.
Sheikh Mohammed Al-Mutawali described these levels in the following lines:
(Then the heavy ones come
with three levels and they are
The one with a fath, then the
dhammah, then the kasrah,
and the saakin follows what preceded it
So
what came before it in a vowel,
then assume for it as a harakah that vowel.)
The Five Levels of Tafkheem
The second school of thought of
tafkheem has five levels. The highest level being a tafkheem letter being
followed by a long alif (for example the in: 
). The
second level is a tafkheem letter with a fathah on it (such as the and in: 
). The
next level that of a tafkheem letter having a dhammah (as in 
).
The next level is a tafkheem letter with a sukoon (for example 
). And
the last level, that of a tafkheem letter with a kasrah (such as the in: 
). This
school of thought as to tafkheem varies from the previous three level school in
a few ways. First, the tafkheem letter with a fathah has two categories, that
of a fath followed by an alif, and then a fathah not followed by an alif. This
school also varies from the previous one in that the tafkheem letter with a
sukoon has its own level of tafkheem, whereas the other school of thought has
the saakin letter following the tafkheem level of the vowel on the letter
preceding it. This means that there will be a difference of tafkheem between
the saakin letters in this group, which are not affected by the vowel of the
letter preceding it, and the other group which is totally affected by the vowel
on the letter preceding it. For example, a saakin tafkheem letter preceded by
a fathah in the three level school of thought, will have the highest ranking of
tafkheem, whereas a saakin tafkheem letter of this five level school of
thought, will have the 4th degree of tafkheem. Ash-Sheikh
Al-Mutawali described the five levels of tafkheem in the following lines:
(and it is said, no the one with
the fat-hah followed by an alif
and after it a fat-hah without an alif
the one with the dhammah, the
saakin, the one with the kasrah;
so that is five, its mention came to you.
and if it is in the lowest level
It has tafkheem, cut off from the istifaal (lowering of the tongue)
So it cannot be said it has tarqeeq
Like its opposite, that is the truth.
Next tidbit lesson, insha' Allah will continue with tafkheem and tarqeeq, moving on to explain the letters that sometimes have tafkheem and sometimes tarqeeq.