What category of ism is it — and why does that decide the ending?

In one line

Definition — al-bina'

Key words in the Arabic

Understand it

Two isms may be in exactly the same state and still not look alike. مُحَمَّدٌ and إِبْرَاهِيمُ are both marfu'; only one carries tanwin. مُسْلِمُونَ and هٰذَا are both marfu'; only one has changed at all.

Nothing has gone wrong. The state is settled by the role. What the ending looks like is settled by the category.

The three primary categories

Every ism falls into one of three: fully declining, partly declining, or non-declining. The category decides how the i'rab is expressed — not what the i'rab is.

The special cases

Seven categories that express i'rab their own way — by letters instead of vowels, or by not showing it at all.

The first division is between the مُعْرَب (mu'rab), the ism whose ending changes, and the مَبْنِيّ (mabni), the ism whose ending does not. The mu'rab then divides again: مُنْصَرِف, which takes tanwin and all three vowels, and مَمْنُوع مِنَ الصَّرْف, which takes neither tanwin nor kasra.

Roughly 85% of isms are fully declining, 13% partly declining, and 2% non-declining. Learn the 85% first and most of the Qur'an is already readable.

Beyond these three sit the special cases — the dual, the two sound plurals, the five nouns, and the isms ending in a fixed alif, ya' or hamza. They express i'rab by letters rather than vowels, or hide it altogether.

How to spot it

Category is not i'rab

Category is not i'rab. This is the single most useful distinction on the whole subject.

A word's i'rab is which of the three states it is in — decided entirely by its role.

A word's category is how it shows that state — decided entirely by what kind of ism it is.

So a kasra proves nothing on its own. هٰذِهِ ends in a kasra in all three states. مَسَاجِدَ takes a fatha in jarr. مُسْلِمَانِ ends in a kasra and is marfu'.

Read the role, then the category. The ending is the last thing you read, not the first.

Related terms

Common questions

If the role already decides the case, why does the category matter?

Because the role tells you which case a word must be in, and the category tells you whether that case will show, and how. Two words in the same role can look entirely different at the end — one takes a vowel, one a letter, one nothing at all.