Both doors contain an Alif after the first root letter, but Bab Tafaa'ul adds one more feature at the beginning.
Key differenceExamplePattern
Inserted Alif onlyقَاتَلَفَاعَلَ
Prefixed تَـ + inserted Alifتَقَاتَلَتَفَاعَلَ
So the prefixed تَـ is the clearest extra marker of Bab Tafaa'ul.
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Derived Trilateral (without Hamzah) - Bab 5: Tafaa'ul (Taqatul)
Both doors contain an Alif after the first root letter, but Bab Tafaa'ul adds one more feature at the beginning.
Key differenceExamplePattern
Inserted Alif onlyقَاتَلَفَاعَلَ
Prefixed تَـ + inserted Alifتَقَاتَلَتَفَاعَلَ
So the prefixed تَـ is the clearest extra marker of Bab Tafaa'ul.