Idgham Rules in Tajweed: Merging Noon Sakinah and Tanween

The idgham rules in Tajweed tell you when a noon sakinah or tanween disappears into the letter that follows it, so that the two are heard as one doubled sound. Six letters trigger it, gathered in the mnemonic word يرملون (yarmaloon), and they divide into four that keep a nasal hum and two that do not. The rule applies across a boundary between two words, which is why a handful of well-known words keep their noon clear.

What merging means in practice

Idgham means to insert one thing into another. Applied to recitation, it means the tongue does not form the noon at all; it goes directly to the position of the next letter and pronounces that letter as if it carried shaddah (the doubling mark). The listener hears no noon, only a strengthened yaa, raa, meem, laam, waw or noon in its place.

Idgham is one of the four outcomes covered in our overview of noon sakinah and tanween. That article gives the map of all twenty-eight letters. This one stays inside the six-letter territory of idgham and looks at the decisions that actually trip readers up: which of the six carry ghunnah, why the rule needs two words, and how to walk through a real phrase.

The six letters and the word that holds them

The letters are yaa (ي), raa (ر), meem (م), laam (ل), waw (و) and noon (ن). Arranged in that order they spell يرملون, pronounced yarmaloon, a word that means nothing in itself and exists purely to be remembered.

Inside that word sits a smaller one. Yaa, noon, meem and waw, rearranged as ينمو (yanmu), are the letters merged with ghunnah (the nasal resonance made in the nose). Laam and raa are the two left over, merged without it. So the real thing to memorise is: six letters, and the four from yanmu hum.

Some teachers also name the two kinds differently: idgham with ghunnah is described as incomplete, because part of the noon, its nasal quality, survives in the merged sound, while idgham without ghunnah is complete, because nothing of the noon remains. Both sets of labels describe the same reading.

With ghunnah and without: what changes in the mouth

Before yaa, noon, meem or waw, the tongue or lips take the position of the coming letter, and while that letter is being formed the nasal passage stays open, so the sound is a merged letter with a hum sitting on top of it. In Surah Al-Jumu'ah (62:9), min yawmil-jumu'ah is read as though written miy-yawmi, the yaa doubled and hummed. In Surah At-Tariq (86:6), min maa'in becomes mim-maa'in. With tanween, khayrun wa abqa in Surah Al-A'la (87:17) is read khayruw-wa abqa.

Before laam or raa, the merge is just as total but the hum is switched off. The tongue goes directly to the laam or the raa, doubles it, and moves on without lingering. Hudan lil-muttaqeen in Surah Al-Baqarah (2:2) is read hudal-lil-muttaqeen. At the end of Surah Al-Ikhlas (112:4), wa lam yakun lahu is read wa lam yakul-lahu. The commonest fault here is carrying the ghunnah habit over from the first group, so that laam and raa are hummed too. Our separate guide to ghunnah and where it belongs explains why that hum has no place on these two letters.

Why the rule needs two words

Idgham of noon sakinah is applied only when the noon ends one word and the merging letter begins the next. Where noon sakinah and one of the six letters meet inside a single word, the noon is read clearly instead. The Quran contains four such words with waw or yaa: dunya (الدنيا), bunyan (بنيان), sinwan (صنوان) and qinwan (قنوان). Teachers call this reading izhar mutlaq, absolute clarity, to distinguish it from the ordinary izhar of the throat letters.

The usual explanation is that merging the noon inside those words would change their shape so much that they could be mistaken for words built on a doubled letter, and the language guards against that confusion. Whatever the reason, the practical instruction is simple: in dunya the noon is heard, and in min yawm it is not.

A decision walk-through with real examples

Take the phrase tanzeelun min rabbil-'aalameen from Surah Al-Waqi'ah (56:80). It contains two decisions in a row.

1. The tanween on tanzeelun is a hidden noon sakinah. The next word begins with meem, one of the yanmu four, and it is a separate word. Merge with ghunnah: tanzeelum-min.
2. The noon of min is followed by raa at the start of rabbi. Raa is one of the six, but not one of the four. Merge without ghunnah: mir-rabbi.

Now a second phrase, from Surah Al-Baqarah (2:48): la tajzee nafsun 'an nafsin shay'an. The tanween on nafsun meets 'ayn, a throat letter, so nothing merges and the noon is clear. The noon of 'an then meets the noon of nafsin: two words, noon into noon, merge with ghunnah. Reading the two decisions one after the other, clear then merged, trains exactly the switch a fluent reader makes without thinking.

Mistakes teachers correct most often

• Humming the laam and raa. The six letters are learned as one word, so many readers treat them as one rule. They are two.
• Half-merging. A faint noon survives before the yaa or waw, so the listener hears a noon and then a doubled letter. Idgham means the noon is gone.
• Merging inside a word. Dunya read as duyya is the classic example, and it is heard often in learners who have just mastered the rule and are applying it everywhere.
• Losing the shaddah. The letter that receives the noon should sound doubled. If it is pronounced lightly, the phrase loses its rhythm and the merge is incomplete in the wrong way.
• Applying it across a stop. If you stop on the word ending in noon, no idgham happens, because there is no next letter to merge into.

Most of these are audible to a listener and invisible to the reader, which is the pattern behind the most common Tajweed mistakes generally.

One last source of confusion is the word itself, because idgham is not reserved for noon. A meem sakinah merges into a following meem in what teachers call idgham shafawi, covered in our article on the rules of meem sakinah, and more advanced study meets idgham between other pairs of similar or neighbouring letters. The concealing rule that borders the noon version, where the noon is neither merged nor clear, is explained in our guide to ikhfa and its fifteen letters.

Frequently asked questions

Does idgham apply to tanween as well as to a written noon?

Yes. Tanween ends in a noon sakinah that is pronounced but not written, so the same six letters trigger the same merge. The only difference is visual: you have to remember that the doubled vowel mark hides a noon.

Why does the mushaf sometimes leave the sukoon off the noon?

In many printed mushafs a noon that is left without its sukoon mark is the printer's way of showing that it is not read clearly, and the following letter often carries a shaddah to show the merge. A noon written with its sukoon before a throat letter, by contrast, signals izhar. Learning to read these conventions speeds up recognition considerably.

Is the ghunnah in idgham held for the same time as in ikhfa?

Teachers describe the length in more than one way, and some rank the strength of ghunnah differently across the rules. Rather than fixing a count from a book, match the length your teacher demonstrates and keep it consistent throughout a passage.

Do the other qira'at merge the same six letters?

Not always. Some readings treat particular letters differently, for example applying or omitting ghunnah in positions where Hafs does the opposite. This article describes Hafs 'an 'Asim only.

How can I tell if I am really merging and not just rushing?

Slow the phrase down. A genuine idgham survives at slow speed: the noon is still absent and the next letter is still doubled. Rushing collapses at slow speed, and the noon reappears.

Practise idgham with someone listening

Reading about six letters is quick; hearing whether your laam is hummed or your dunya is merged takes another pair of ears. The Tajweed course pairs you with a teacher who corrects these merges inside your own recitation, and you can book a free one-to-one trial class to have a page of your choice checked before committing to anything.