Feminine second-person forms directly address one woman, two women or a group of women. The singular and plural endings differ from masculine forms, whereas the dual form is shared.
TypeFirst formSecond form
Singularفَعَلْتِ: you (one female) did.فُعِلْتِ: you were acted upon.
Dualفَعَلْتُمَا: you two women did.فُعِلْتُمَا: you two were acted upon.
Pluralفَعَلْتُنَّ: you women did.فُعِلْتُنَّ: you women were acted upon.
ـتِ indicates singular feminine address and ـتُنَّ feminine plural address. فَعَلْتُمَا alone cannot identify gender, because both dual addressee forms are identical.