While trilateral (three-letter) roots dominate Arabic, there exists a smaller but important category of quadrilateral roots — roots consisting of four consonant letters. These verbs and their derivatives follow their own set of patterns and are worth studying for a complete understanding of Arabic morphology.
Base Pattern
The base quadrilateral verb follows the pattern فَعْلَلَ (fa'lala), where ل appears twice but represents two different root letters. Using the root د-ح-ر-ج as an example:
- Past: دَحْرَجَ (he rolled something).
- Present: يُدَحْرِجُ (he rolls something).
- Masdar: دَحْرَجَة (rolling).
- Active Participle: مُدَحْرِج (one who rolls).
- Passive Participle: مُدَحْرَج (something rolled).
Common Quadrilateral Verbs
- تَرْجَمَ (he translated) — from root ت-ر-ج-م.
- زَلْزَلَ (he shook/caused an earthquake) — from root ز-ل-ز-ل.
- بَعْثَرَ (he scattered) — from root ب-ع-ث-ر.
- وَسْوَسَ (he whispered/tempted) — from root و-س-و-س.
Quadrilateral verbs also have an augmented form, تَفَعْلَلَ, which often indicates a reflexive or passive meaning: تَدَحْرَجَ (it rolled by itself), تَزَلْزَلَ (it was shaken). This parallels the relationship between Form I and Form V in trilateral verbs.
While less common than trilateral verbs, quadrilateral roots include some very frequently used words, especially in modern Arabic. Studying them completes your understanding of the Arabic root-and-pattern system.