The removal of the final (ن) is the marker of the jussive case of the imperfect verb if it follows the pattern of the five verbs:
1. تَفْعَلِينَ
Ex. لَا تَكْسَلِي أَيَّتُهَا الطَّالِبَةُ عَنْ أَدَاءِ وَاجِبَاتِكَ.
تَكْسَلِي is an imperfect verb in the jussive case whose mark is the removal of the final (ن) before the introduction of the particle of the jussive case تَكْسَلِينَ
2. تَفْعَلَانِ
Ex. لَا تَكْسَلا أَيُّهَا الطَّالِبانِ عَنْ أَدَاءِ وَاجِبَاتِكُما.
تَكْسًلا is an imperfect verb in the jussive case whose mark is the removal of the final (ن) before the introduction of the particle of the jussive case تَكْسَلانِ
3. يَفْعَلَانِ
Ex. سَيَنْدَمُ الوالِدانِ إذا لَمْ يَتَعاوَنَا عَلَى تَرْبِيَةِ أَبْنَائِهِما.
يَتَعَاوَنَا is an imperfect verb in the jussive case. The mark here is the removal of the final (ن) before the introduction of the particle of the jussive case يَتَعَاوَنَانِ
4. تَفْعَلُونَ
Ex. لَا تَقْبَلُوا الظّلْمَ يَسُودُ في وَطَنِكُمْ، أَيُّهَا اَلشَّبَابُ.
تَقْبَلُوا is an imperfect verb in the jussive case. The mark here is the removal of the final (ن) before introduction of the particle of the jussive case تَقْبَلُونَ
5. يَفْعَلُونَ
Ex. لا يُكَرَّمُ العُمّالُ إذا لَمْ يُتْقِنُوا عَمَلَهُمْ.
يُتْقِنُوا is an imperfect verb in the jussive case. The mark here is the removal of the final (ن) before the introduction of the particle of the jussive case يُتْقِنُونَ
The final (ن) is removed from each imperfect verb that follows one of these patterns and which is in the jussive case.
