Proceded by either who, what, why, when, where, whether or how, this ending connects a clause the requires additional information. Corresponds to ‘whether or not A/V’ in certain cases.
너무 맛있었어요! 어떻게 만들었는지 가르쳐 주세요.
It was delicious! Please tell me how you made it.
여자 친구가 있는지 없는지 궁금해요.
I wonder whether he has a girlfriend.
청소하는지 쉬는지 잘 모르겠어요.
I don’t know whether she is cleaning or resting.
내일 날씨가 더운지 알아요?
Do you known whether tomorrow’s whether will be hot?