Masculine second-person forms address one man, two men or a group of men. They use different endings from the third-person forms.
TypeFirst formSecond form
Singularفَعَلْتَ: you (one male) did.فُعِلْتَ: you were acted upon.
Dualفَعَلْتُمَا: you two did.فُعِلْتُمَا: you two were acted upon.
Pluralفَعَلْتُمْ: you men did.فُعِلْتُمْ: you men were acted upon.
The endings ـتَ، ـتُمَا، ـتُمْ distinguish singular, dual and plural. The vowel pattern inside the stem changes with voice, but person and number stay constant.