The Jussive Mood and Defective Verbs
To negate an action in the past, use the particle لم (did not) followed by a present-tense verb. This puts the verb into the jussive mood.
For most regular verbs, the jussive mood changes the final vowel to a sukun. However, for defective verbs (which end in a weak letter like ي or ى), the final weak letter drops entirely.
For example, يكفي (it suffices) drops its final ي after لم:
| The salary was not enough this month. | الراتب لم يكف هذا الشهر.ar-râtibu lam yakfi hâdhâ ash-shahra |
Dropping the Alif Maqsura (ى)
The same rule applies to verbs ending in an alif maqsura (ى). The verb ينسى (he forgets) drops the final ى after لم, leaving the fatha intact on the preceding letter (لم ينس).
| He did not forget the debt. | لم ينس الدين.lam yansa d-dayn |
Longer Defective Verbs
This dropping rule applies to all defective verbs, regardless of length. Verbs like يشتري (he buys) and يعطي (he gives) also lose their final ي when placed after لم.
| He did not buy a car because he wants to save money. | لم يشتر سيارة لأنه يريد أن يوفر المال.lam yashtari sayyâratan li'annahu yurîdu an yuwaffira al-mâla. |
| He did not give his friend the amount. | لم يعط صديقه المبلغ.lam yu'ti sadîqahu l-mablagha |
Using the Jussive with "I"
The final weak letter drops in the jussive mood regardless of the subject prefix (أ، ن، ي، ت). When conjugating for "I" (أنا), the verbs أنسى (I forget) and أشتري (I buy) drop their endings just like the "he" and "she" forms.
| I did not forget the budget. | لم أنس الميزانية.lam ansa al-mîzâniyyah. |
| I did not buy the shirt because it is expensive. | لم أشتر القميص لأنه مكلف.lam ashtari l-qamîsa li-annahu mukallifun |
Summary
Whenever a defective verb is preceded by لم, remember to drop the final weak letter.
| He did not forget the debt, but he spent the salary. | لم ينس الدين لكنه صرف الراتب.lam yansa d-dayna lakinnahu sarafa r-râtiba |
