The process can be understood in 4 steps:
1. The initial ت of the original pattern is made silent.
2. It changes to match the first root letter.
3. The matching letters merge, producing Shaddah.
4. A Kasrah-bearing Hamzat-ul-Wasl is added at the beginning so pronunciation does not start with a silent consonant.
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How the Assimilation Happens
Derived Trilateral - Bab 8: If'aal & Bab 9: If'il (Assimilation Doors)
The process can be understood in 4 steps:
1. The initial ت of the original pattern is made silent.
2. It changes to match the first root letter.
3. The matching letters merge, producing Shaddah.
4. A Kasrah-bearing Hamzat-ul-Wasl is added at the beginning so pronunciation does not start with a silent consonant.