Different suffixes distinguish third person from second person and first person even within a single root.
Word / formMeaning / explanation
ضَرَبَhe struck.
ضَرَبْتَyou (male singular) struck.
ضَرَبَتْshe struck.
ضَرَبْتِyou (female singular) struck.
ضَرَبْتُI struck.
Note the positions of sukūn and the short vowels: ضَرَبَتْ has final tāʾ with sukūn, whereas ضَرَبْتَ has a vowelless bāʾ and a fatḥah on tāʾ. Similar letters do not make the same form.