Grammar term · I'rab · The signs
Build-vowel (mabni 'ala fath/damm/kasr)
'alamat al-bina' (al-haraka)
عَلَامَة الْبِنَاء (الْحَرَكَة)
I'rabThe signscore term
In one line
The fixed vowel a mabni word is “built on” — described as mabni 'ala al-fath, al-damm or al-kasr.
Classical definition
وَكُلُّ حَرْفٍ مُسْتَحِقٌّ لِلْبِنَا وَالأَصْلُ فِي الْمَبْنِيِّ أَنْ يُسَكَّنَا وَمِنْهُ ذُو فَتْحٍ وَذُو كَسْرٍ وَضَمُّ كَأَيْنَ أَمْسِ حَيْثُ وَالْسَّاكِنُ كَمْ
“Every harf deserves to be built, and the rule for a built word is that it be given a sukun; yet among them is one built on a fatha, one on a kasra and one on a damma.”
Understand it
When an analysis says حَيْثُ is “built on damm” or أَيْنَ “built on fath”, it names the vowel that permanently ends the word. It looks like an i'rab marker but is not one: no governor caused it and none can change it. The phrase مَبْنِيٌّ عَلَى الْفَتْحِ in i'rab is simply the formal way of recording that fixed vowel.
How to spot it
Recognition test
The same final vowel in every sentence, whatever the word's job — a build-vowel, not i'rab.
In the Qur'an
قُلْ هُوَ ٱللَّهُ أَحَدٌ
Al-Ikhlas 112:1 — “Say: He is Allah, the One and Only;”
هُوَ is built on a fatha — that is the vowel it keeps in every position. A mabni word is described by the vowel it is fixed on, not by a state it moves through.
Study this ayah word by word →Related terms
Common questions
What is the difference between being built on a fatha and being in nasab?
Everything. A word in nasab was put there by something and could be moved by something else. A word built on a fatha keeps that vowel whatever happens around it, because it has no case to move through in the first place.
Next in the guideعَلَامَة ظَاهِرَةApparent (zahira) marker →Updated