قَاضٍ is related to قَاضِي. In the regular indefinite nominative and genitive forms, the final yāʾ is dropped and a kasra tanwīn remains.
The spelling of جَاءَ قَاضٍ and مَرَرْتُ بِقَاضٍ is the same, but the former is nominative and the latter genitive.
Caution: Kasra tanwīn here does not prove that the noun is genitive; check its syntactic role.
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Noun Case Class 8 — The Manqūṣ Noun
قَاضٍ is related to قَاضِي. In the regular indefinite nominative and genitive forms, the final yāʾ is dropped and a kasra tanwīn remains.
The spelling of جَاءَ قَاضٍ and مَرَرْتُ بِقَاضٍ is the same, but the former is nominative and the latter genitive.
Caution: Kasra tanwīn here does not prove that the noun is genitive; check its syntactic role.