Zaynab has four letters, so it does not meet the triliteral condition. It remains a diptote.
Hind is triliteral, its middle consonant is vowelless, and it is not foreign; both declensions are permitted.
Simply lacking a visible feminine tāʾ does not make their grammatical treatment identical.
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Causes of Diptote Status — Femininity and Its Conditions
Zaynab has four letters, so it does not meet the triliteral condition. It remains a diptote.
Hind is triliteral, its middle consonant is vowelless, and it is not foreign; both declensions are permitted.
Simply lacking a visible feminine tāʾ does not make their grammatical treatment identical.