In the five inflected imperfect patterns, an indicative inflectional nūn appears at the end. The jussive imperative removes this nūn, while the dual alif, masculine plural wāw and second-person feminine singular yāʾ remain.
Word / formMeaning / explanation
تَفْعَلَانِ → اِفْعَلَاyou two do.
تَفْعَلُونَ → اِفْعَلُواyou men do.
تَفْعَلِينَ → اِفْعَلِيyou (female singular) do.
The rule does not delete every final letter. Specifically, the inflectional nūn is removed, preserving signs of number and gender.