Lam negates an imperfect verb but transfers the meaning to past time. The verb following lam is jussive (majzūm).
يَفْعَلُ ← لَمْ يَفْعَلْ — he did not do.
يُفْعَلُ ← لَمْ يُفْعَلْ — it was not done to him/it.
Compare لَنْ يَفْعَلَ (final fatḥa) with لَمْ يَفْعَلْ (final sukūn); the two must not be pronounced alike.
Although the verb is morphologically imperfect, lam makes the complete construction past-negative.
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Lam governs the jussive
Negating the Imperfect with Lan and Lam: Subjunctive, Jussive and Full Paradigms
Lam negates an imperfect verb but transfers the meaning to past time. The verb following lam is jussive (majzūm).
يَفْعَلُ ← لَمْ يَفْعَلْ — he did not do.
يُفْعَلُ ← لَمْ يُفْعَلْ — it was not done to him/it.
Compare لَنْ يَفْعَلَ (final fatḥa) with لَمْ يَفْعَلْ (final sukūn); the two must not be pronounced alike.
Although the verb is morphologically imperfect, lam makes the complete construction past-negative.