In Korea, age is given precedence over all other considerations. When conversing with someone of a higher rank or age, formal language must be used. Similarly, when conversing with a junior/someone younger, you can use informal language (banmal, ). Unless two people agree to use banmal at the same time, this usually remains the case. Even in a k-pop group with members who are mostly around the same age, a few months difference in birthdate can make a big difference.