Common mistakes
The middle radical is و or ي. It stretches into a long vowel: قَالَ: and shortens before a consonant ending and in the jussive: قُلْتُ, لَمْ يَقُلْ.
صَوَمَ → صَامَ Past: heصَوَمَتْ → صَامَتْ Past: sheصَوَمْتَ → صُمْتَ Past: you (m.)صَوَمْتُ → صُمْتُ Past: I