Compare kataba → katabat (sound-final) with ramā → ramat and daʿā → daʿat (weak-final): all show feminine agreement, but the weak-final forms lose alif.
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Sound-Root and Weak-Root Comparison
Feminine Tāʾ in the Past Tense: Form and Agreement
Compare kataba → katabat (sound-final) with ramā → ramat and daʿā → daʿat (weak-final): all show feminine agreement, but the weak-final forms lose alif.