Grammar term · I'rab · i'rab
السُّكُون
al-sukun
Sukun marker
I'rab · i'rabI'rab marker (alama)core term37,412+ in the Qur'an
In one line
The sukun — the “no vowel” sign; 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.”
(الآجرّومية)
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.
Related terms