When to use class in Korean
Korean: 수업[ su-eop ]

When to use it
수업 (class) means a lesson or class time at school or an academy. You use it when talking about studying with a teacher, like an English class or math class. It can mean one class today or classes in general.
Example sentences
오늘 수업은 아홉 시에 시작해요.
Today's class starts at nine o’clock.
지금 수업 중이에요.
I am in class now.
수업 전에 숙제를 했어요.
I did my homework before class.
엄마, 오늘 수업이 정말 재미있었어요.
Mom, today's class was really fun.
공원에서 미술 수업을 해요.
We have art class in the park.
여행 중에도 온라인 수업을 들어요.
I take online classes even while traveling.