Severity, Moderation and Looseness: The Three Letter-Weight Rules in Tajweed (UK Guide)

The three weights of Arabic letters in Quranic recitation

Every Arabic letter, when recited in the Quran, carries one of three "weights" — heaviness (tafkhīm), lightness (tarqīq), or a position somewhere between depending on context. The classical tajweed terms British Muslim children encounter for these are shiddah (severity / heaviness), tawassuṭ (moderation / middle), and rikhwah (looseness / lightness). Understanding which letters belong to which category — and how to physically produce the corresponding weight — is one of the foundations of authentic Quranic recitation.

This guide is the British Muslim parent's reference for the weight system: the categories, the letters in each, the physical mechanics, the rules for letters whose weight changes by context, and the most common mistakes British learners make.

The two parallel classifications

Classical tajweed actually has two related but distinct classifications of letter weight. British Muslim families encounter both terminology systems and often confuse them.

Classification 1 — by airflow restriction (the "severity / moderation / looseness" axis)

This classification looks at how completely the airflow stops when the letter is pronounced.

Category	What it means	The letters
Shiddah (severity)	Complete stoppage of airflow at the point of articulation	أ ج د ق ط ب ك ت — eight letters, collected in the mnemonic ajidu qaṭṭu bakat
Tawassuṭ (middle)	Partial restriction — air flows somewhat	ل ن ع م ر — five letters, collected in li-na-ʿu-mar
Rikhwah (looseness)	Free flow of air, no real restriction	The remaining 15 letters — ث ح خ ذ ز س ش ص ض ظ غ ف ه و ي

This classification is mostly descriptive — it tells you the physical nature of how each letter is produced. It does not directly change how British learners "should" pronounce the letter; rather, it explains what they are doing physically.

Classification 2 — by acoustic weight (the "tafkhīm / tarqīq" axis)

This classification — much more practically important for daily recitation — looks at whether the letter is heard as "heavy" (full, dark, throat-resonant) or "light" (thin, bright, forward).

Category	The letters
Always heavy (tafkhīm)	Seven letters — خ ص ض غ ط ق ظ — collected in the mnemonic khuṣṣa ḍaghṭin qiẓ
Always light (tarqīq)	The majority of the remaining letters
Conditional	The letters ا ل ر — heavy or light depending on context

The seven heavy letters in detail

These are the letters British learners most commonly under-pronounce, producing recitation that sounds correct in vocabulary but flat in weight.

Letter	Name	Example
خ	khā	خَلَقَ — the kh sound from the back of the throat, fully heavy
ص	ṣād	الصَّمَدُ — the heavy s, distinct from the light سـ
ض	ḍād	الضَّالِّينَ — the unique Arabic letter; full elongation along the side of the tongue
غ	ghayn	الْمَغْضُوبِ — the throat ghain, like a French r but deeper
ط	ṭā	الصِّرَاطَ — the heavy t, with the tongue making a flat contact
ق	qāf	قُلْ — the deep q, from the very back of the throat, distinct from the lighter ك
ظ	ẓā	الظَّالِمِينَ — the heavy version of dh, with the tongue between the front teeth and resonating with weight

If your child pronounces any of these seven letters with the same lightness as their English-influenced consonant equivalents, their recitation has a foundational problem that needs targeted correction.

The three conditional letters

Alif (ا)

The alif takes the weight of the letter before it. If the preceding letter is one of the seven heavy letters, the alif is heavy. If the preceding letter is light, the alif is light. Example: in قَالَ the alif is heavy because the preceding qāf is heavy. In كَانَ the alif is light because the preceding kāf is light.

Lām (ل) — particularly in the name "Allāh"

The lām is generally light, but the lām of the divine name Allāh has a special rule: it is heavy when preceded by a fatḥa or ḍamma vowel, light when preceded by a kasra. So "qāla Allāhu" has a heavy lām, but "bismi-llāhi" has a light lām. This single rule, applied consistently, is one of the most audible markers of trained vs untrained recitation.

Rāʾ (ر)

The most complex of the three. The rāʾ is heavy in some contexts and light in others according to a specific set of rules involving the surrounding vowels. The general principle:

• Rāʾ with fatḥa or ḍamma — heavy
• Rāʾ with kasra — light
• Rāʾ with sukūn — depends on the preceding vowel
• Rāʾ at the end of a word being stopped on — depends on the preceding letter and vowel

The full set of rules takes a few weeks to internalise but, once mastered, becomes second nature.

Common British learner mistakes

1. Flat ḍād. The most common single mistake — pronouncing the ḍād as a flat heavy d rather than producing the elongation along the side of the tongue. Particularly common in British Muslim children of South Asian heritage where the inherited sound is closer to a heavy d.
2. Soft qāf. Pronouncing the qāf as a kāf — losing the deep throat resonance. Particularly common in British Muslim children who have grown up hearing recitation from family members rather than from qualified reciters.
3. Substituting ẓā with z or dh. The ẓā has a distinct heavy quality; substituting it loses the weight.
4. Light lām in "Allāhu". Failing to apply the heavy lām rule when reciting the divine name in the appropriate vowel context.
5. Flat alif following heavy letters. Producing a flat English-style "ah" rather than letting the alif inherit the heaviness of the preceding letter.
6. Inconsistent rāʾ. Treating all rāʾs the same regardless of vowel context.

How British Muslim children typically learn the weight system

Stage	Typical age	What is covered
Foundation	5-7	Recognising the letters and basic pronunciation
Heavy/light awareness	7-9	Introducing the seven always-heavy letters; physical practice
Conditional letters	9-11	Alif inheritance, the lām of Allāh, basic rāʾ rules
Mastery	11-14	Full rāʾ rules; Sajāwandī classification understanding; consistent application
Hifz refinement	14+	Hafiz-level reciter quality with reliably correct weight throughout

A British Muslim child who has been correctly taught the weight system by age 12 will recite for life with the dignity the Quran deserves. A child who has not been corrected by then will need significantly more remedial work later.

Why the weight system matters spiritually

The weight categories are not pedantry. The Prophet ﷺ said: "Recite the Quran with the lahn (musical accent) of the Arabs" (al-Bayhaqī). The weight system is precisely what makes Quranic Arabic sound different from English-influenced flat speech. It carries the dignity of the divine speech as it was originally heard. A British Muslim child who recites with proper weight is participating in the unbroken oral tradition of authentic Quranic recitation; a child who does not is — through no fault of their own — disconnected from that tradition.

Correction is achievable. One-to-one work with a qualified teacher will identify the specific weight problems in any given reciter's pronunciation and address them in a few months of focused work.

Frequently asked questions

Where to go next

For more on tajweed at Eaalim, see our guides on Tajweed UK, Qalqalah and the Five Letter Qualities, Waqf Rules, Al-Madd, and Quran Recitation. To begin one-to-one tajweed correction with an Al-Azhar-graduate teacher trained in classical recitation, book a free trial lesson.