Lam: active | passive
FormActivePassive
Second-person fem. singularلَمْ تَفْعَلِيلَمْ تُفْعَلِي
Second-person fem. dualلَمْ تَفْعَلَالَمْ تُفْعَلَا
Second-person fem. pluralلَمْ تَفْعَلْنَلَمْ تُفْعَلْنَ
The second-person feminine singular تَفْعَلِينَ becomes لَمْ تَفْعَلِي, losing inflectional nūn while keeping yāʾ. The feminine dual loses nūn as well, but the feminine plural keeps its own nūn.
لَمْ تَفْعَلِي — you (one woman) did not do.
لَمْ تَفْعَلْنَ — you women did not do.
Both constructions negate a past action despite using imperfect prefixes.