Key Takeaways
- Whenever a noon sakinah or tanween is followed by another letter, exactly one of four rules applies, decided entirely by which letter comes next.
- Izhar means pronouncing the noon sound clearly, used before six throat letters.
- Idgham means merging the noon sound into the next letter, either with or without a nasal sound depending on the letter.
- Iqlab converts the noon sound into a light meem sound, and applies only before the letter baa.
- Ikhfa hides the noon sound with a light nasal quality, covering the remaining fifteen letters, which makes it the most common of the four rules.
When a noon sakinah or tanween is followed by another letter, exactly one of four rules applies: Izhar, Idgham, Iqlab, or Ikhfa. Which rule applies is decided entirely by the letter that comes next, and together the four rules cover all 28 letters of the Arabic alphabet with no overlap.
The System: One Noon or Tanween, Four Possible Rules
This is one of the more structured parts of Tajweed, since it works like a complete system rather than a loose collection of exceptions. Every letter in Arabic falls into exactly one of four groups, and the group determines exactly what happens to the noon sakinah or tanween sound that precedes it. Learning the letter groups is most of the work here, since the rule itself follows automatically once you know which group a letter belongs to.
Izhar: Clear Pronunciation
Izhar means pronouncing the noon sound clearly and fully, without any nasal blending into the next letter. It applies when a noon sakinah or tanween is followed by one of six throat letters: ء ه ع ح غ خ. Because these letters are produced from deep in the throat, keeping the noon sound distinct and separate is the clearest way to pronounce them together.
Idgham: Merging Into the Next Letter
Idgham means merging the noon sound into the letter that follows, rather than pronouncing them as two separate sounds. This splits into two versions depending on the letter involved.
- Idgham with ghunnah, before ي ن م و, where the merge keeps a light nasal sound.
- Idgham without ghunnah, before ل ر, where the merge is complete, with no nasal sound carried through.
Both versions blend the noon into the following letter, but the presence or absence of the nasal quality is what distinguishes them.
Iqlab: Converting to a Meem Sound
Iqlab is the smallest of the four categories, applying to exactly one letter: baa (ب). When a noon sakinah or tanween is followed by baa, the noon sound is converted into a light meem sound, carried with a soft nasal quality. This is a genuine conversion rather than a blend, the sound actually becomes a meem for that moment, distinct from both Izhar and Idgham.
Ikhfa: Concealing With a Nasal Sound
Ikhfa covers the remaining fifteen letters: ت ث ج د ذ ز س ش ص ض ط ظ ف ق ك. Here, the noon sound is neither pronounced clearly (as in Izhar) nor fully merged (as in Idgham). Instead, it's partially concealed, held with a light nasal quality that sits between the two. Because fifteen letters trigger this rule, Ikhfa is by far the most frequently applied of the four, which makes it one of the rules students end up practising the most simply through regular exposure.
How to Actually Learn Which Rule Applies
Trying to memorise all 28 letters and their groupings in one sitting tends to overwhelm beginners. A more practical approach is learning one rule and its letters at a time, practising it specifically in short surahs, before moving to the next. Over a few weeks, recognising the correct rule for a given letter becomes automatic rather than something you consciously work out mid-recitation.
This full system is usually covered as part of a structured Tajweed course, once basic letter pronunciation from Noorani Qaida is solid. A free trial lesson is a good way to find out exactly where your own recitation currently stands before working through it properly with a teacher.