Root Letters and Added Letters

Derived Trilateral (with Hamzah) - Bab 1: Ifti'aal (Ijtinab)

In اِجْتَنَبَ, separate the root from the additions.

LettersType
ج، ن، بOriginal root letters
اِ، تAdded letters

So the root is ج-ن-ب, while the pattern adds Hamzat-ul-Wasl at the beginning and ت after the first root letter.