"The teacher is sitting."
Translation:선생님이 앉아 있어요.
-고 있다 is attached to verbs that take objects. - 있다 is attached to verbs that do not.
기린은 하루에 약 두시간을 잔다. ← 麒麟은 하루에 約 두時間을 잔다.
- “Giraffes sleep for about two hours a day.”
추위 때문에 잠을 잘 수 없다.
- “Because of the cold, I can’t sleep.”
- “I need to take a nap.”
단잠을 자고 있었어.
- “I slept like a baby.”
- “I slept well.”
- “I had a great sleep.”
In English, sleep can be used intransitively. “I slept two hours” is understood as “I slept for two hours.” There is no object in that sentence at all. But even in English, it can be used transitively:
- “I slept the night away.“
but sleeping doesn't take objects so why is it 자고 있어요?
Sure it does: 어제 밤에 잠을 잘 잤습니까?
Here’s another example: 단잠을 자고 있었어.
It literally means I slept a sweet sleep. And sleep is transitive in this English sentence as well!
-아/어/해 있다 is used to express the continuous state of a COMPLETED action; can only be used with intransitive verbs (no object)
As such, I think a better English translation would be "The teacher is SEATED".
선생님이 앉고 있어요. The teacher is sitting down. (He has not sat down yet, still in the process of sitting down. He is still bending his knees, and his butt is moving closer to the chair.)
선생님이 앉아 있어요. The teacher is seated.
The verb: "to sit" is intransitive, meaning it does not take a direct object. Kevin Li has already explained this, but 있다 is used after intrasitive verbs, while -고 있다 is used after transitive verbs.