Permissible and obligatory are not synonyms. A permissible substitution may coexist with the wāw-initial form, whereas an obligatory substitution applies when its narrowly specified conditions are satisfied.
Wāw formHamzah formCondition
وُجُوهٌأُجُوهٌInitial wāw with ḍamma
وِشَاحٌإِشَاحٌInitial wāw with kasra
Do not invent unattested alternatives for every word merely because the structural resemblance is superficial.
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Miscellaneous Morphological Explanations: Eight Rules for Wāw, Yāʾ, Alif and Hamzah
Permissible and obligatory are not synonyms. A permissible substitution may coexist with the wāw-initial form, whereas an obligatory substitution applies when its narrowly specified conditions are satisfied.
Wāw formHamzah formCondition
وُجُوهٌأُجُوهٌInitial wāw with ḍamma
وِشَاحٌإِشَاحٌInitial wāw with kasra
Do not invent unattested alternatives for every word merely because the structural resemblance is superficial.