يَدْعُو → لَمْ يَدْعُ
Translation: He calls → he did not call.
لَمْ governs the jussive and negates past occurrence. The final root wāw drops in the singular لَمْ يَدْعُ, leaving a ḍammah before the deleted consonant.
لَمْ يَدْعُوَا — the two did not call.
لَمْ يَدْعُوا — the men did not call.
In these dual/plural cases it is the indicative nūn ending that drops. Do not confuse this with final-root deletion in the singular.
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The Particle لَمْ: Jussive and Weak-Letter Deletion
Defective Wāw Verb: Full Paradigm of دَعَا يَدْعُو with Morphological Explanations
يَدْعُو → لَمْ يَدْعُ
Translation: He calls → he did not call.
لَمْ governs the jussive and negates past occurrence. The final root wāw drops in the singular لَمْ يَدْعُ, leaving a ḍammah before the deleted consonant.
لَمْ يَدْعُوَا — the two did not call.
لَمْ يَدْعُوا — the men did not call.
In these dual/plural cases it is the indicative nūn ending that drops. Do not confuse this with final-root deletion in the singular.