Common mistakes
The root ends in و or ي, and the endings themselves change. Three patterns cover it: دَعَا يَدْعُو, رَمَى يَرْمِي and نَسِيَ يَنْسَى.
شَكَوَ → شَكَا Past: heشَكَوَتْ → شَكَتْ Past: sheشَكَوُوا → شَكَوْا Past: they (m.)يَشْكُوُ → يَشْكُو Present: he