What relationship is shown by طَمْأَنَهُ فَاطْمَأَنَّ?

Final Characteristics of Derived Forms: Ifʿīlāl, Ifʿilāl, Faʿlala, Tafaʿlala, and Related Patterns

• A change of color
• Causing reassurance followed by becoming reassured
• Omission of all subjects
• Accusative by a preposition