As a term, Al 'Idhlâq is that the pronunciation of the letter lies on the tip of the tongue or the tip of the lip.

It is called Al 'Idhlâq (literally "the end") because some letters are articulated on the tip of the tongue:

these are the letters ر (Râ '), ل (Lâm), ن (Nûn).

Others use the tip of the lip, these are the letters ب (Ba '), ف (Fâ'), م (Mîm).

These letters produced at the end, at the end of the phonatory and expiratory apparatus are like doors opened on the outside which make it possible to articulate the sounds produced more deeply!

In Arabic, Al 'Ismât means impediment.

As a term, it is a heaviness of the pronunciation of the letter when it is not in contact with Al 'Idhlâq's letters.

It is thus called(impediment or impossibility) because it is impossible to find these letters alone in roots of quadrilateral words such as جعفر (ja'far) or roots composed of five letters such as سفرجل (safarjal).

It is mandatory to find in this type of words one or more letters "mudhlaqa" (of Al'Idhlâq) to offset the heaviness of these letters by the lightness of the letters of Al'Idhlâq.

If such words do not contain letters from Al 'Idhlâq,

you can then deduce that these words have appeared in the Arabic language but are not of Arab origin, as noted by Arabic grammarians.

Technically, the letter does not use the tip of the tongue or lip, and they are articulated in the deep and inner part of the vocal tract!

The letters of Al'Ismat are twenty-three, they are the letters of the abjadia (the alphabet) after having removed the six letters of Al 'Idhlâq.

الشدة

Ash Shiddah

This term literally means in Arabic "Retention", "total stop"!

Technically, Ash-Shidda is an obstruction of the flow of the voice (sawt) during the pronunciation of the letter due to a solid support of the articulation point.

Certain letters, certain sounds, in the absence of vowels have the characteristic of absorbing totally the sound flow. 

This is due in part to the "occlusive" character of these letters.

A bit like a handbrake shot pulled dry and that would completely absorb the speed and therefore the energy:

 total stop of the vehicle, total stop of the breath!

It is interesting to note that Al Jahr is the obstruction of the flow of breath, while AlShidda is the obstruction of the flow of the voice.

It is therefore important to distinguish these two characteristics!

Thus, one can compare by pronouncing "السماء" (As-samâ'i, which means 'the sky');

do you see how the voice and the breath are obstructed together because the hamza (ء) is an intense letter (Shadîd) and sounded (majhûr, of "Jahr", without breath) at the same time.

now pronounce "كتبك" (Kitabak, which means 'your book'), then you notice in the pronunciation of the letter 'Kâf' that the voice is obstructed but that the flow of the breath continues.

Thus, the letter 'Kaf' is a letter having the characteristic of Ash-Shidda (total stop of the sound) and Al Hams (presence of breath) but not Al Jahr(no breath)!

The total stop of the sound occurs for the letters:

Alef (ا), Jiim (ج), Dal (د), Qaf (ق), Taa (ط)

Ba (ب), Kaf (ك), Ta (ت).

البينية

Al Bayniyyah

This term literally means in Arabic"highlighting", "clarification" because the two phenomena, retention and flow of sound are present!

Technically, the letters possessing this characteristic are defined as "intermediate" (tawassut) because the voice is not obstructed as it is with the letters of Al Shidda (total stop of the sound), and it does not flow completely like when articulating the letters of Ar-Rakhâwa (total flow of sound).

Thus, for the letters concerned by this distinctive feature, in the absence of a vowels, the sound will flow partially, a little as if the total retention of the flow was impossible and an air escape occurrs!

This characteristic concerne the sounds and thus,the letters:

Lam (ل), Noun (ن), Eain (ع), Miim (م) and Ra (ر).

الاستعلا

Al Isti ' la

This term literally means in Arabic "The Elevation";

This painting has for object of inspiration the elevation upwards that take the sound during the articulation of certain letters.

They are called letters of Al Isti'la.

Technically, Al 'Isti'lâ' is the elevation of the tongue towards the palate during the pronunciation of the letter.

Note concerning AL-Isti'lâ 'and at-tafkhîm (emphasis):

the letters of Al Isti'lâ imply the emphasis (At tafkhîm).

So it is necessary to define what At Tafkhîm means and its different levels.

Al-'Istifal is opposed to al-'Isti'lâ ', it implies thinning (at-tarqîq).

At-tafkhîm means in the Arabic language the emphasis, the amplification.

As a term, it is an emphasis given to the letter by filling the mouth with its resonance.

At-tarqiq means in the Arabic language thinning,

As a term, it is a thinning given to the letter and which is characterized by a sharper sound!

For all the letters below, the sound goes towards the palate:

The Khã(خ), the Saad(ص), the Dåd(ض), the 3ayn(ع), the Rayn(غ)

The Taa (ط), the Qaaf (ق), and the Zaa (ظ);

These letters are always emphatic, it is a specific articulatory trait: the emphasis,

The sound produced is "deeper" than the corresponding non-emphatic sound.

It is obtained by modifying the shape of the buccal resonator by increasing the dorso-palatine cavity by flattening the middle of the tongue, creating more space in the mouth increasing the dept of the sound!

There is five level of emphasis (Tafkhîm):

When the letter of al-'isti'lâ has a fatha (vowel 'a') and it precedes an Alif (ا) as in the name "خالد" (Khālîd).

When the letter of al-'isti'lâ contains a fatha and it is not preceded by an Alif (ا) as in the word "ظلمتم" (Dhalamtoum, which means' you have been unfair',' you have darkened').

When the letter of al-'ist'lâ has a dhamma (vowel 'u') as in the word "قل" ("Qûl", which means "say").

When the letter of al-'isti'lâ carries a sukûn (small circle placed on the letter to indicate the absence of vowel), as in the word "اقترب" (Iqtarib, which means "get closer").

And finally, when the letter of al-'Isti'lâ 'includes a kasra (vowel' i '), as in the word "اقيم" (Aqîm, which means 'set up!' or 'established').

One might think that this last level is thinned (muraqqaq), which is a mistake.

Certainly, the fifth level of tafkhîm is emphatic, more than is the highest level of tarqîq (thinned and therefore more acute, sharper).

Specific rules concerning the letters Alef(ا), Lam (ل), and Ra (ر):

These letters, when they are pronounced, are sometimes emphatic, thus directing their sound towards the palate and under other conditions they are softened then the sound does not go towards the palate.

Thus for the letter Alef (ا), the sound is directed towards the palate and is carried out emphatically when it is preceeded by the letters:

Kha (خ), Saad (ص), Daad (ض), Eain (غ), Taa (ط), Qaaf (ق), Zaa (ظ) and the letter Ra (ر).

On the other hand, the sound does not go towards the palate and is made thinned preceded by all other letters, therefore the sound is not emphatic.

This is due to the phenomenon known as 'Contagion'. 

Often the presence of an emphatic consonant in a word "contaminates" the consonantal and vocalic environment, and the whole syllable is pronounced emphatically!

Concerning the letter Lam (ل), and only when pronouncing the Name Allah الله:

The sound is not directed towards the palate and the letter is thinned when it is preceded by the sound "e" (called Al Kasrah in Arabic );

On the other hand, the sound goes towards the palate and is pronounced emphatically if preceded by the sound "u" (called Ad dammah in Arabic )

or preceded by the sound "a" (called Al Fathah in Arabic).

Specific case concerning the letter Ra(ر):

emphatic

The letters are always pronounced in an emphatic way and the sound is directed towards the palate in the following eight cases:

When the letter is sanctioned by the vowel "a" (Fathah);

 When the letter that precedes the Ra (ر) carries a Fathah and that it is devoid of any vowels (called "As soukoun" in Arabic);

When the antepenultimate (two times before the last) letter carries a Fathah and the one that follows and the letter Ra (ر) are deprived of vowels;

When the Ra (ر) carries the vowel "u" (Dammah);

When the last letter carries a Dammah and the Ra (ر) at the end of the word carries a Sukoun;

When the antepenultimate letter carries a Dammah (vowel"u") and the following one, followed by the letter Ra (ر) are sanctioned by a Soukoun(the graphic representation of the absence of vowels is a small circle on the letter concerned);

When the letter Ra (ر) in the second position in the word carries a Sukoun and is preceded by " Hamzatoul wasl" (ا) which corresponds to the vowel "a" in "capital" to designate the beginning of the word;

When the letter Ra (ر) in the absence of all vowels is followed by an emphatic letter with a Fathah( vowel "a") and is preceded by a letter bearing the vowel "e"( called al kasrah, and corresponding to the vowel "i")

If you don't understand what i am saying just enjoy the view...i mean the pictures, the drawing...

 Thinned

In the following four cases, the letter Ra(ر) is always pronounced in a thinned manner and the sound does not move towards the palate:

When the letter Ra (ر) carries the vowel "i"( sounding "e" like in the word "free" in english);

When the letter Ra (ر) in the middle of two letters carries a Soukoun(absence of vowel) and is preceded by a letter bearing the vowel "i" (Kasrah) and followed by a thinned letter;

When the letter Ra (ر) at the end of the word carries a Sukoun preceded by a thinned letter bearing also a Sukoun and whose antepenultimate letter carries the vowel "i(Kasrah);

When the letter Ra (ر) at the end of the word is devoid of a vowel (Soukoun) and preceeded by the letter Ya(ي) bearing a Soukoun( absence of vowel).

الاستفال

Al Istifal

This representation is inspired by letters whose sound is not directed towards the palate during their articulation.

Technically, as a term, al-istifal is the lowering of the tongue during the pronunciation of the letter.

The letters of al-Isifal are twenty-one in number.

These letters are:

Ba(ب), Ta(ت), Tha(ث), Jiim(ج). Ha(ح), Dal(د)

 Zal(ذ), Za (ز), Siin (س), Shiin (ش), Eain (ع), Fa (ف), Kaf (ك), Miim (م), Noun (ن), Ha (ه), Waou (و), and the Ya (ي).

These letters are always thinned during their articulation, the flow is constant and without emphasis.

الانفتاح

Al Infitah

This term literally means in Arabic

"The Opening", "The Release".

Technically, Al'Infitah consists of separating the tongue from the palate so that the air propagates during the pronunciation.

The sound is not compressed between the tongue and the palate, it flows fluidly for the rest of the letters, namely:

Alef(ا), Ba(ب), Ta(ت), Tha(ث), Jiim (ج), Ha(ح), Kha(خ), Dal(د), Zay(ز), Siin (س), Shiin(ش), Eain(ع), Rain(غ), Fa(ف), Qaaf(ق), Kaf(ك), Noun(ن), Ha(ه), Waou(و) and Ya(ي).