Verbs Ending in a Weak Letter

Defective verbs are a vital part of Arabic because many common verbs like 'to walk', 'to call', and 'to forget' follow this pattern. The behavior of these verbs is governed by the underlying root letter and the verb's pattern.

1. Past Tense Forms:
Defective verbs in the past tense fall into two main categories:

• Alif-ending: These end in a straight Alif (ا) or Alif Maqsura (ى), representing an underlying و (waw) or ي (yaa). Examples: دَعَا (to call) and رَمَى (to throw).
• Visible Yaa-ending: These follow the فَعِلَ pattern and end in a visible ي. Examples: نَسِيَ (to forget) and بَقِيَ (to remain).

2. The Present Tense (Indicative):
In the present tense, the final weak letter appears as a Waw, Yaa, or Alif Maqsura depending on the verb:

• Waw: يَدْعُو (He calls)
• Yaa: يَرْمِي (He throws)
• Alif Maqsura: يَنْسَى (He forgets)

3. The Subjunctive Mood:
In the subjunctive mood (after particles like أَنْ or لَنْ), the endings behave differently:

• For Waw and Yaa endings, a visible Fatha appears: لَنْ يَدْعُوَ (He will not call), لَنْ يَرْمِيَ (He will not throw).
• For Alif Maqsura endings, the vowel remains hidden: لَنْ يَنْسَى (He will not forget).

4. Conjugation Changes:
When adding suffixes that start with a consonant (like -tu for 'I'):

• For Alif-ending verbs, the Alif 'returns' to its original root letter: دَعَا ← دَعَوْتُ (I called).
• For visible Yaa-ending verbs, the ي remains: نَسِيَ ← نَسِيتُ (I forgot).

When adding the feminine suffix -at (she):

• For Alif-ending verbs, the weak letter is deleted: دَعَا ← دَعَتْ (She called).
• For visible Yaa-ending verbs, the ي remains: نَسِيَ ← نَسِيَتْ (She forgot).

When adding the dual suffix:

• The weak letter is preserved: دَعَوَا (They two called) and نَسِيَا (They two forgot).

When adding the plural suffix -ū (they):

• The weak letter is deleted for all types. However, the vowel on the second radical changes based on the verb pattern:
• For fa‘ala verbs (دَعَا), the Fatha is retained: دَعَوْا (They called).
• For fa‘ila verbs (نَسِيَ), the Kasra changes to a Damma to match the Waw: نَسُوا (They forgot).

5. The Jussive Mood and Imperative:
In the jussive mood (after particles like لَمْ) and the imperative, the final weak letter is dropped completely:

• يَرْمِي (He throws) ← لَمْ يَرْمِ (He did not throw)
• يَنْسَى (He forgets) ← لَمْ يَنْسَ (He did not forget)

6. The Active Participle (اسم الفاعل):
The active participle of defective verbs undergoes a unique change when indefinite and in the nominative or genitive cases. The final weak letter is dropped and replaced by tanwīn kasra:

• قَاضِي (judge) becomes قَاضٍ (a judge).
• مَاشِي (walker) becomes مَاشٍ (a walker).
• Note: The ي returns if the word is definite: القَاضِي.