Rule 4 concerns a broken plural where two wāws or two yāʾs occur after the plural alif in the relevant internal configuration; one of them becomes hamzah.
أَوَّلٌ → أَوَائِلُ
Translation: First → first ones.
خَيِّرٌ → خَيَائِرُ
Translation: Good / choice → good or choice ones.
The book supplies أَوَاوِلُ as the underlying shape for the first plural. The instructional point is the introduction of hamzah in the specified weak-letter cluster.
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Rule 4: Wāw/Yāʾ After the Plural Alif
Miscellaneous Morphological Explanations: Eight Rules for Wāw, Yāʾ, Alif and Hamzah
Rule 4 concerns a broken plural where two wāws or two yāʾs occur after the plural alif in the relevant internal configuration; one of them becomes hamzah.
أَوَّلٌ → أَوَائِلُ
Translation: First → first ones.
خَيِّرٌ → خَيَائِرُ
Translation: Good / choice → good or choice ones.
The book supplies أَوَاوِلُ as the underlying shape for the first plural. The instructional point is the introduction of hamzah in the specified weak-letter cluster.