Why students are calling their teacher Mr. Kim? Isn't it rude?
Native speaker’s answer
Rebecca
There's some language that uses "teacher" to address someone. But in English, "teacher" is a title that cannot be used when calling someone. You need to say "Mr. Kim" or "Mrs. Kim". In comparison, you can call a professor by "Professor Steve" at university. Professor is used as both a title and a way of addressing someone.