Tanwīn — The Double Vowel Ending
The -un, -an, -in endings found only on nouns — what tanwin signals, and the famous things it does NOT signal.
What Is Tanwīn?
Tanwīn (تَنْوِين) — often called "nunation" — is the double vowel ending on Arabic words: ـٌ (-un), ـً (-an), ـٍ (-in). The doubled mark is pronounced with an "n" sound that is never written as a letter: كِتَابٌ is read kitābun. It is one of the most visible features of vowelled Arabic text, and one of the most informative.
What Tanwīn Tells You
It marks an ism. Tanwīn is one of the three exclusive signs of the ism — you will never see it on a verb or a particle. Spot tanwīn and you have identified the word type instantly.
It shows the i'raab. The three forms of tanwīn map directly onto the three cases: ـٌ is raf', ـً is nasab, ـٍ is jarr. In an indefinite noun, tanwīn is where the case lives: جَاءَ رَجُلٌ (a man came — raf'), رَأَيْتُ رَجُلًا (I saw a man — nasab), مِنْ رَجُلٍ (from a man — jarr).
Tanwīn appears only on isms. ـٌ = raf' · ـً = nasab · ـٍ = jarr. Tanwīn and أَلْ never appear on the same word: add al- → remove the tanwīn. مُسْلِمٌ → الْمُسْلِمُ
What Tanwīn Does NOT Tell You
The common shortcut "tanwīn = indefinite" is a misunderstanding worth correcting early:
Many definite words carry tanwīn — proper nouns such as مُحَمَّدٌ and نُوحٌ are definite (they name specific people, Step 1 of definiteness) yet end in tanwīn. And many indefinite words have no tanwīn — the ghayru munsarif (partly-declining) nouns such as أَكْبَرُ (greater) and مَسَاجِدُ (mosques) never take tanwīn at all, and show kasra as fatha in jarr. This category includes most names of the prophets: إِبْرَاهِيمُ، يُوسُفُ، فِرْعَوْنُ.
Definiteness is determined by the seven categories of definite ism — NOT by the presence or absence of tanwīn.
Tanwīn in Grammar Rules You Already Know
Several structures hinge on tanwīn behaviour. Adding أَلْ removes it. The mudaf of an idafah drops its tanwīn (رَسُولُ اللهِ — never رَسُولٌ اللهِ). And the lā of categorical negation is recognised precisely by its absence: لَا رَيْبَ — an indefinite noun in nasab without tanwīn — is the signature of "no doubt whatsoever".
Quranic Example
Frequently Asked Questions
How is tanwin pronounced if the noon is never written?
The doubled vowel mark itself carries the "n": كِتَابٌ = kitābun, كِتَابًا = kitāban, كِتَابٍ = kitābin. In pause (waqf), the tanwīn is dropped — nasab tanwīn becomes a long ā, which is why ـً is usually written on an added alif: كِتَابًا read in pause as kitābā.
Why do some Quranic names never take tanwin?
They belong to the ghayru munsarif (partly-declining) category — most foreign-origin proper nouns, many broken plural patterns, and certain word shapes. They never take tanwīn and show fatha instead of kasra in jarr: مِنْ إِبْرَاهِيمَ, not إِبْرَاهِيمٍ.
Is tanwin ever added to a word with al-?
Never — the two are mutually exclusive. أَلْ and tanwīn both occupy the "definiteness slot" of the word, so adding the article always removes the tanwīn: مُسْلِمٌ → الْمُسْلِمُ. Seeing either one (but never both) is also a quick confirmation that the word is an ism.