For example, you are a 20 year old male/female. You are walking on the street, then you see a male stranger who seems to be the same age as your. He is in hurry, you see him drop his wallet. You pick ...
I have sometimes wondered what would be the appropriate way of addressing (fellow) students that are junior to oneself. Given name? Full name? Name + 妹/第? Are there even cases where one can use 哥/兄 ...