The Prohibitive Verb (Fi'l Nahi) - Concept & Construction

1. What Is Fi'l Nahi?

Fi'l Nahi is used to forbid an action in the future.
Examples: لَا تَنْصُرْ = Do not help! • لَا تَضْرِبْ = Do not hit!
The key idea is simple: a Mudhaari' form is used with the prohibitive particle and becomes jussive.

2. How to Form the Prohibitive

Start from the Mudhaari' form, place the prohibitive particle before it, then apply Jazm.

ResultStep
تَنْصُرُstart from Mudhaari'
لَا تَنْصُرْadd prohibitive Laa + apply Jazm

Core rule: prohibitive Laa + Mudhaari' in Jazm.

3. Prohibitive Laa Is Governing

Prohibitive Laa gives Jazm to the Mudhaari' verb. Its visible effect follows the familiar 5 + 7 + 2 map.

EffectForms
final Dhammah becomes Sukoon5
Noon-e-I'raabi drops7
visible ending remains unchanged2 feminine plural forms

Check: 5 + 7 + 2 = 14.

4. See Jazm in Real Forms

The same prohibitive rule appears differently according to the Mudhaari' ending.

ProhibitionMudhaari'Change
لَا يَنْصُرْيَنْصُرُfinal Dhammah → Sukoon
لَا تَنْصُرُوْاتَنْصُرُوْنَNoon-e-I'raabi drops
لَا يَنْصُرْنَيَنْصُرْنَvisible ending unchanged

5. Negation and Prohibition Are Not the Same

The same particle can appear in two different uses. Look at the verb ending to tell them apart.

MeaningFormUse
he does not helpلَا يَنْصُرُNegation; no Jazm
let him not helpلَا يَنْصُرْProhibition; Jazm
you do not helpلَا تَنْصُرُوْنَNegation; Noon remains
do not helpلَا تَنْصُرُوْاProhibition; Noon drops

6. Command and Prohibition: One Important Difference

In an active addressed command, the Mudhaari' prefix is removed. In prohibition, the Mudhaari' form keeps its prefix and takes prohibitive Laa.

ResultMeaningType
اِضْرِبْHit!Command
لَا تَضْرِبْDo not hit!Prohibition

So the addressed prohibition keeps the initial Mudhaari' marker.

7. Practice with Three Roots

Apply the same rule to different verbs.

ProhibitionCommandMeaning
لَا تَنْصُرْاُنْصُرْhelp
لَا تَضْرِبْاِضْرِبْhit
لَا تَسْمَعْاِسْمَعْlisten

The command changes its beginning, while the prohibition keeps the Mudhaari' prefix and adds prohibitive Laa.

8. A Simple Recognition Map

When you see Laa before a Mudhaari' verb, check the ending:
• ending unchanged → it may be simple negation
• Sukoon or Noon-drop → it is the prohibitive use taught here
Then read the meaning as forbidding an action.
Core pattern: لَا تَنْصُرْ = Do not help!