With weak-final perfect verbs, attaching the silent feminine tāʾ may delete the final weak letter. For example, ramā becomes ramat, not ramāt.
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Weak-Final Verbs and Deletion
Feminine Tāʾ in the Past Tense: Form and Agreement
With weak-final perfect verbs, attaching the silent feminine tāʾ may delete the final weak letter. For example, ramā becomes ramat, not ramāt.