Rule of Past Absolute Negation with "Lam" (لَمْ) & Weak Letters

1. What Does Lam Do?

Lam is a governing particle used before a Mudhaari' verb.
Its meaning changes the present/future form into a negative past meaning.
Example:
يَفْعُلُ
He does / he will do.
لَمْ يَفْعُلْ
He did not do.
So the verb is still a Mudhaari' form, but its meaning becomes past negative.

2. Lam Makes the Mudhaari' Jussive

Lam is a jussive particle.
Across the 14-form Mudhaari' grid, its structural effect falls into three groups:

What happensForms
final Dhammah becomes Sukoon5
Noon-e-I'raabi drops7
form remains unchanged2

Check: 5 + 7 + 2 = 14.

3. Group 1: Five Forms Take Sukoon

Five forms normally end with Dhammah. After لَمْ, that final Dhammah becomes Sukoon.

After LamBefore Lam
لَمْ يَفْعُلْيَفْعُلُ
لَمْ تَفْعُلْتَفْعُلُ — feminine Ghaa'ib singular
لَمْ تَفْعُلْتَفْعُلُ — masculine Haadhir singular
لَمْ أَفْعُلْأَفْعُلُ
لَمْ نَفْعُلْنَفْعُلُ

Rule: Dhammah → Sukoon in these 5 positions.

4. Group 2 and 3: Noon Drops in Seven; Two Stay Unchanged

The remaining nine positions follow the same structural split already seen in the previous Mudhaari' rules:
• 7 forms lose Noon-e-I'raabi
• 2 feminine plural forms remain unchanged
Examples:
يَفْعُلَانِ → لَمْ يَفْعُلَا
يَفْعُلُونَ → لَمْ يَفْعُلُوا
تَفْعُلِينَ → لَمْ تَفْعُلِي
But:
يَفْعُلْنَ → لَمْ يَفْعُلْنَ

5. What Are the Weak Letters?

The source identifies three weak letters:
ا — Alif
و — Waaw
ي — Yaa
For the rule in this level, pay special attention when a Mudhaari' verb ends in a weak letter.
If لَمْ makes that ending jussive, the final weak letter is deleted instead of simply receiving a visible Sukoon.

6. Three Weak-Ending Examples

After LamBefore LamWeak ending
لَمْ يَدْعُيَدْعُوWaaw
لَمْ يَرْمِيَرْمِيYaa
لَمْ يَخْشَيَخْشَىfinal alif maqsurah form

In each example, the final weak ending is removed when the verb becomes jussive after لَمْ.

7. Sound Ending or Weak Ending?

Before applying the jussive rule, first check the final root letter.

Result after LamEnding type
final Dhammah becomes Sukoonsound final
final weak letter is deletedweak final

So:
يَفْعُلُ → لَمْ يَفْعُلْ
يَرْمِي → لَمْ يَرْمِ

8. The Main Rule to Remember

Remember four things:
• لَمْ changes Mudhaari' meaning to negative past.
• 5 sound-ending positions take Sukoon.
• 7 forms lose Noon-e-I'raabi; 2 feminine plural forms remain unchanged.
• if the jussive ending is a weak letter, that weak letter is deleted.
Core map:
5 + 7 + 2 = 14