Grammar term · I'rab · The signs
Sukun marker
al-sukun
السُّكُون
I'rabThe signscore term
In one line
The sukun (سُكُون) is the “no vowel” sign, and as an i'rab marker it signals jazm on the present verb.
Classical definition
وَأَمَّا السُّكُونُ فَيَكُونُ عَلَامَةً لِلْجَزْمِ فِي الْفِعْلِ الْمُضَارِعِ الصَّحِيحِ الْآخِرِ.
“The sukun is the marker of jazm in the present verb whose final letter is sound.”
Key words in the Arabic
الصَّحِيح الْآخِرsound-ending — not ending in ا، و or ي
Understand it
Thousands of sukuns sit inside words doing nothing grammatical; the one that matters for i'rab sits on the last letter of a mudari' after a jazm-causer: لَمْ يَكْتُبْ. If the verb's last letter is weak, elision takes the sukun's place — the definition's “sound-ending” clause is what reserves the sukun for verbs like يَكْتُبُ.
How to spot it
Recognition test
Find the jazm-causer first (لَمْ، لَا النَّاهِيَة، إِنْ…); the sukun on the verb after it is the marker.
In the Qur'an
لَمْ يَلِدْ وَلَمْ يُولَدْ
Al-Ikhlas 112:3 — “He begetteth not, nor is He begotten;”
لَمْ is a jazm-causer, and يَلِدْ answers it by going silent at the end. That silence is the sukun, and on the present verb it is the marker of jazm.
Study this ayah word by word →Related terms
Common questions
Is a sukun really a case marker?
It marks the absence of a vowel, and that is exactly the point. Jazm is the state in which the ending is taken away, so the absence itself is the sign. It belongs to the verb alone — an ism is never majzum.
Next in the guideوَاو الْجَمَاعَةPlural waw (subject) →Updated