In وَضَعَ — يَضَعُ, the root is و ض ع: wāw first, ḍād second, and ʿayn third.
يَوْضَعُ → يَضَعُ
Ḍād itself is not the relevant guttural; the final ʿayn is. The imperfect has fatḥah on the middle radical and the quiescent initial wāw drops.
This and يَهَبُ illustrate two placements of the guttural condition: second radical in one root, third radical in the other.
Opening interactive controls...
The Guttural in وَضَعَ
Weak-Initial Roots: Elision, Substitution, Assimilation and Short Paradigms
In وَضَعَ — يَضَعُ, the root is و ض ع: wāw first, ḍād second, and ʿayn third.
يَوْضَعُ → يَضَعُ
Ḍād itself is not the relevant guttural; the final ʿayn is. The imperfect has fatḥah on the middle radical and the quiescent initial wāw drops.
This and يَهَبُ illustrate two placements of the guttural condition: second radical in one root, third radical in the other.