Grammar
-지?
Question to oneself
Form
Verb or adjective stem + -지?; noun + -(이)지? — “... again? / I wonder ...?”
Function
The ending -지? expresses a question asked to oneself, a check or an attempt to recall something. 어디지? means “Where is this?”
Why this form?
-아/어? asks a more direct question.
-나요? is suitable for a polite question to another person.
Forms That Should Not Be Confused
- -아/어? asks more directly, without making the reflection quite as apparent.
이게 뭐야? — What is it? ?
2. -인가요? is polite; it is more appropriate for a conversation partner than for casual thought.
어디인가요? — Where is it located? ?
Examples
여기가 어디지? — Where am I again? ?
내일이 무슨 요일이지? — What day is it already? Tomorrow. ?