-지 => a sentence ending for a soft confirmation, question, or a suggestion.
* In an indicative sentence.
1. a soft confirmation of something, as if talking to oneself.
- 당연하지: that's as expected (no surprise there).
- 그럴 순 없지: There is no way we can do that = We can't do that.
- 그 시절엔 다들 그렇게 살았지: That's how everyone lived in those days.
2. mentions (with a disappointment, reproach, etc) what one wishes to have happened but did not in reality.
- 에이, 더 일찍 오지: Well, you should have come earlier.
- 저런, 조심하지: Gee, you should have been more careful.
* In an interrogative sentence.
1. asks a question looking for a confirmation of what one thinks.
- 뭐지?: What's that (as if saying to oneself)? (The nuance is softer than 뭐야?, which is similar)
- 날씨가 좋지?: It's a fine day, isn't it?
- 이제 희망이 없지?: Our hopes are dashed, aren't they.
2. gently suggests an action to another person.
- 이제 그만 가지?: Let's get going, shall we?
- 내 말대로 하지?: Why don't you do as I suggest?