First, you need to know a "verb root" - sorry, I don't know the correct term for this. It's easily done: just deduct Х and a vowel before it from dictionary form of the verb (the original from verbs are written in dictionaries). For example: сурах - сур ах, авах - ав ах, өгөх - өг өх, ирэх - ир эх, болох - бол ох Past tense = verb root + caн / сэн / сон / сөн depending on the verb type For example: сур+сан = сурсан, ав+сан=авсан, ир+сэн=ирсэн, бол+сон=болсон, өг+сөн=өгсөн Future tense = verb root + на / нэ / но / нө depending on the verb type For example: сур+на=сурна, ав+на=авна, ир+нэ=ирнэ, бол+но=болно, өг+нө=өгнө