What is nasab (al-nasab), and what is a mansub word?
In one line
Definition — the four divisions of i'rab
Key words in the Arabic
Understand it
نَصْب (nasab) is the name of the state; مَنْصُوب (mansub) is what you call a word standing in it.
For most isms nasab shows as a fatha — مُسْلِمًا (musliman), الْمُسْلِمَ (al-muslima). When the word is indefinite and carries two fathas, an alif is written after it — كِتَابًا — except after a ta' marbuta (جَنَّةً) or after an alif with hamza (سَمَاءً).
What puts a word in nasab
Twelve roles put an ism into nasab — more than either of the other two states, which is why nasab is the longest chapter of any nahw book.
Other categories express nasab by letters instead: the dual with ـَيْنِ, the sound masculine plural with ـِينَ, the sound feminine plural with a kasra — مُسْلِمَاتٍ — and the five nouns with an أَلِف.
How to spot it
In the Qur'an
In the language — فِي اللُّغَة
The word نَصْب (nasab) in everyday Arabic means setting a thing upright, standing it straight.
نَصَبَ الْخَيْمَةَ (nasaba al-khaymata) — “he pitched the tent”
As a grammatical term it means the state whose sign is the upright stroke above the letter, the fatha, and what stands in place of it.
Related terms
Common questions
Why are there twelve roles causing nasab and only two causing jarr?
Because nasab is where Arabic puts everything that is neither the pillar of the clause nor governed by a preposition. Objects, states, reasons, times, specifications and exceptions all land there, so the list is long by necessity.
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