When to use professor in Korean
Korean: 교수[ gyo-su ]

When to use it
A professor (교수) is a teacher at a college or university. This word is used when you talk about someone who teaches university students. It does not mean a teacher in elementary, middle, or high school.
Example sentences
우리 학교 교수는 친절해요.
The professor at our school is kind.
저는 오늘 교수와 이야기해요.
I talk with the professor today.
교수는 지금 강의실에 있어요.
The professor is in the classroom now.
제 언니는 대학에서 교수를 만났어요.
My older sister met a professor at the university.
아버지는 비행기에서 교수를 만났어요.
My father met a professor on the plane.
저는 서점에서 교수가 쓴 책을 샀어요.
I bought a book written by a professor at the bookstore.