Everyone says "senior" and "senior". Am I using it correctly?

Post it on the fifth floor is a casual remark.

In terms of language expression habits, it is more intimate to call "Senior Sister", because you are from the same school and she is a senior, so it is the most "appropriate" to call Senior Sister, which not only shows respect but also intimacy, and narrows the distance between us.

For "senior", as the one on the first floor said, it is generally used to describe a male senior. If it is used to describe a female senior, it can only be said if it is relayed to others. If you write directly to the parties, it will make people feel embarrassed, uncomfortable, too formal and too rigid.

So it's better to use senior.