جُوْرُ, a city name in the established example, has three letters and a sakin middle. It is obligatorily ghayr munsarif here because foreign proper-name status supplies the additional cause. Compare: هِنْدٌ / هِنْدُ permits both treatments, while جُوْرُ is diptote by foreignness.
Opening interactive controls...
Case Three: A Foreign Name
Cause of Ghayr Munsarif: Feminine Alif and Feminine Proper Names
جُوْرُ, a city name in the established example, has three letters and a sakin middle. It is obligatorily ghayr munsarif here because foreign proper-name status supplies the additional cause. Compare: هِنْدٌ / هِنْدُ permits both treatments, while جُوْرُ is diptote by foreignness.