جُبَّةٌ (cloak) has the sound feminine plural جُبَّاتٌ.
Nominative: الْجُبَّاتُ; accusative: الْجُبَّاتِ; genitive: الْجُبَّاتِ.
In the book’s example al-jubbāti is an accusative accompaniment complement; its kasra is the regular accusative marker of this plural class.
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Al-Mafʿūl Maʿahu: Accompaniment and Coordination
جُبَّةٌ (cloak) has the sound feminine plural جُبَّاتٌ.
Nominative: الْجُبَّاتُ; accusative: الْجُبَّاتِ; genitive: الْجُبَّاتِ.
In the book’s example al-jubbāti is an accusative accompaniment complement; its kasra is the regular accusative marker of this plural class.