The book gives six classes for unaugmented triliteral verbs. Recognize the vowel on the middle radical, particularly in the imperfect:
ClassPerfectImperfectExample
Naṣaraفَعَلَيَفْعُلُنَصَرَ يَنْصُرُ
Ḍarabaفَعَلَيَفْعِلُضَرَبَ يَضْرِبُ
Samiʿaفَعِلَيَفْعَلُسَمِعَ يَسْمَعُ
Fataḥaفَعَلَيَفْعَلُفَتَحَ يَفْتَحُ
Karumaفَعُلَيَفْعُلُكَرُمَ يَكْرُمُ
Ḥasibaفَعِلَيَفْعِلُحَسِبَ يَحْسِبُ
The key diagnostic is the vowel of the second radical (ʿayn), not merely the initial consonant.
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Properties of the Six Basic Triliteral Forms: Contest, Transitivity, and Semantic Patterns
The book gives six classes for unaugmented triliteral verbs. Recognize the vowel on the middle radical, particularly in the imperfect:
ClassPerfectImperfectExample
Naṣaraفَعَلَيَفْعُلُنَصَرَ يَنْصُرُ
Ḍarabaفَعَلَيَفْعِلُضَرَبَ يَضْرِبُ
Samiʿaفَعِلَيَفْعَلُسَمِعَ يَسْمَعُ
Fataḥaفَعَلَيَفْعَلُفَتَحَ يَفْتَحُ
Karumaفَعُلَيَفْعُلُكَرُمَ يَكْرُمُ
Ḥasibaفَعِلَيَفْعِلُحَسِبَ يَحْسِبُ
The key diagnostic is the vowel of the second radical (ʿayn), not merely the initial consonant.