Hello everyone! I often see various greeting words but actually I don't know their accurate meanings and the difference of them. Greeting words which I've seen: What's up? What's going on? What are you going? What are you going on? How are you doing? How are you going? How are you going on? How's it going? How's it going on? Could you tell me the accurate meaning of each sentence? I think not each sentence has the same meaning of "How are you?" and I guess some of them are grammatically correct. I expect your answer. Thank you!