When to use to understand in Korean
Korean: 납득하다[ nap-deuk-ha-da ]

When to use it
납득하다 means to understand something and feel that it makes sense. You use it when you hear a reason or explanation and accept it. It is common for rules, decisions, prices, and other situations where you say, “Okay, I understand now.”
Example sentences
엄마가 왜 화났는지 이제 납득해요.
Now I understand why Mom was upset.
선생님 설명을 듣고 납득했어요.
I understood after hearing the teacher's explanation.
친구가 늦은 이유를 듣고 납득했어요.
I understood after hearing why my friend was late.
이 신발이 왜 비싼지 납득해요.
I understand why these shoes are expensive.
기차가 늦는 이유를 듣고 납득했어요.
I understood after hearing why the train was late.
네 설명을 듣고 다 납득했어요.
I understood everything after hearing your explanation.