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.
تَمَنَّيَ → تَمَنَّى Past: heتَمَنَّيَتْ → تَمَنَّتْ Past: sheتَمَنَّيُوا → تَمَنَّوْا Past: they (m.)يَتَمَنَّيُ → يَتَمَنَّى Present: he