1. You Already Know
2. Yes, Definitely, Maybe, Quite Possibly, Probably, Most Likely, It was Alright
3. An affirmative response that's definition varies depending on the tone used while speaking the word
4.. The word can be used to agree, as a greeting, an answer, a definition of a feeling

It depends on your tone completely, on campus we all say it regardless of the subject because we can relate it to many things and you know what people are talking about because as the definition says: you already know