Nūn Sākinah and Tanwīn: Four Rules Explained

There is a moment every new tajweed student encounters: you are reading along and you reach a nūn with a sukūn over it, or a word ending in tanwīn, and you suddenly cannot remember what to do with the sound. Do you say it clearly? Blend it? Drop it entirely? The answer depends entirely on one thing — the letter that comes immediately after it.

The good news is that every Arabic letter is covered by one of exactly four rules, and once you know which group each letter belongs to, the decision becomes automatic. This article walks through all four rules — Iẓhār, Idghām, Iqlāb and Ikhfā' — with Qur'anic examples you can look up and listen to, memory aids for the letter groups, and the mistakes that catch beginners most often. If you are learning with a teacher, bring this alongside your lessons — rules understood on paper are different from rules applied in recitation.

What Are Nūn Sākinah and Tanwīn?

A Nūn Sākinah is the letter Nūn (ن) carrying a sukūn (ْ), written as نْ. It produces a clear 'n' sound and can appear in the middle or at the end of a word. Tanwīn refers to the double vowel markings at the end of nouns: two fatḥas (ـً), two kasras (ـٍ), or two ḍammas (ـٌ). Though they look like double vowels, they are pronounced by adding an 'n' sound to the vowel — -an, -in, or -un. Because they are phonetically identical, both are governed by the same four rules.

Rule 1: Iẓhār — Clear Pronunciation

Iẓhār (إِظْهَار) means clarity or manifestation. When a Nūn Sākinah or tanwīn is followed by one of six specific letters, the nūn sound is pronounced clearly and fully — no merging, no nasalisation, no change. These six letters are called the Ḥalqī (throat) letters because they are all articulated from the throat.

The reason for Iẓhār is physical: the nūn is articulated at the tip of the tongue, and the six throat letters are produced deep in the throat. The distance between the two points makes merging them phonetically impossible — so each sound stays separate and clear.

Here the Nūn Sākinah in مَنْ is followed by Hamzah (ء) in آمَنَ. Because Hamzah is an Iẓhār letter, the nūn is pronounced fully and clearly before moving to the next word.

Rule 2: Idghām — Merging

Idghām (إِدْغَام) means merging or assimilation. When a Nūn Sākinah or tanwīn is followed by one of six letters, the nūn sound blends into the following letter — almost as if the nūn disappears. The six letters are remembered using the mnemonic word يَرْمَلُونَ (yarmalūn), whose six letters are: ي – ر – م – ل – و – ن.

Idghām with Ghunnah (Nasal Sound)

Four of the six letters — Yā (ي), Nūn (ن), Mīm (م), and Wāw (و) — trigger an Idghām with a nasal sound (ghunnah) lasting two counts. These four are collected in the mnemonic يَنْمُو (yanmū). The nūn merges into the following letter while a nasal resonance is held through the nose for approximately two beats.

The Nūn Sākinah in مِنْ is followed by Nūn (ن) — one of the يَنْمُو letters — so Idghām with Ghunnah applies. The two nūns merge into one nasalised sound held for two counts. The same applies with the other يَنْمُو letters, as in مِن يَعْمَلْ (Yā), مِن مَّاءٍ (Mīm) and مِن وَلَدٍ (Wāw).

Idghām without Ghunnah

The remaining two Idghām letters — Lām (ل) and Rā (ر) — produce merging without any nasal sound. The nūn disappears completely into the following letter, and the sound comes entirely from the mouth.

The tanwīn (ـٌ) on غَفُورٌ is followed by Rā (ر), so Idghām without Ghunnah applies. It is pronounced Ghafūr-ur-Raḥīm — not Ghafūrun Raḥīm. No nasal sound is held; the nūn simply vanishes.

Critical Exception: Iẓhār Muṭlaq

Rule 3: Iqlāb — Conversion

Iqlāb (إِقْلَاب) is the simplest of the four rules because it involves only one letter: Bā (ب). Whenever Bā follows a Nūn Sākinah or tanwīn, the nūn sound is converted into a Mīm (م) sound, and a ghunnah of two counts is applied. The lips come together as they would for Mīm, and the nasal resonance is held before releasing into the Bā.

In some printed muṣḥafs, a small Mīm (ۢ) is written above the Nūn to signal this conversion — a helpful visual cue for learners. Whether the Nūn Sākinah is inside a word or at the end of one word before another word beginning with Bā, the rule is the same.

Here the Nūn Sākinah and Bā are within the same word. The nūn is converted to a Mīm sound with ghunnah — you do not say an-bi'hum but rather am-bi'hum with a nasal quality. The same conversion applies across two words, as in مِنْ بَعْدِ (min ba'di), where the nūn takes on a Mīm sound before the Bā.

Rule 4: Ikhfā' — Concealment

Ikhfā' (إِخْفَاء) means concealment or hiding. If any of fifteen letters follows a Nūn Sākinah or tanwīn, the nūn is neither fully pronounced nor fully merged — it is hidden. The tongue does not touch the palate or upper front teeth; there is a slight gap. A nasal sound (ghunnah) of approximately two beats is produced through the nose while the mouth prepares for the following letter.

The fifteen Ikhfā' letters are: ت – ث – ج – د – ذ – ز – س – ش – ص – ض – ط – ظ – ف – ك – ق. These are the letters remaining after the six Iẓhār letters, six Idghām letters, and one Iqlāb letter have been accounted for — meaning all 28 Arabic letters are now assigned.

The Nūn Sākinah in مِنْ is followed by Jīm (ج), one of the fifteen Ikhfā' letters. The nūn is concealed: the tongue stays away from the palate, and a nasal resonance is produced for roughly two counts as the mouth positions itself for the Jīm.

The Complete Picture: All 28 Letters Assigned

A Note on Ghunnah

Three of the four rules involve ghunnah — the nasal sound produced when air streams through the nasal cavity. Its standard duration is two ḥarakāt (two beats), roughly the time it takes to tap your finger twice at a measured pace. Ghunnah also appears independently whenever you encounter a Nūn with a shaddah (نّ) or a Mīm with a shaddah (مّ) — as in إِنَّ and ثُمَّ. In those cases, a two-count ghunnah is always applied regardless of what follows.

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