This is a weak-middle verb: the second root letter is و.
Because the middle root is weak, the written forms do not look exactly like a sound-root example of the same underlying pattern.
The lesson highlights this exception with forms such as كُدْتَّ and تَكَادُ.
So learn two things separately: the underlying Bab pattern, and the actual surface forms used by this weak verb.
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Why the Surface Form Looks Different
Trilateral Bare Irregular - Bab 3: Kada Yakadu & Weak Roots
This is a weak-middle verb: the second root letter is و.
Because the middle root is weak, the written forms do not look exactly like a sound-root example of the same underlying pattern.
The lesson highlights this exception with forms such as كُدْتَّ and تَكَادُ.
So learn two things separately: the underlying Bab pattern, and the actual surface forms used by this weak verb.