I wish you can understand german, because since I learnd german, i have almost English that I learnd forgotten.... It's very hard for me in English that to explain, but I i will have a try. Frankly speaking, in Korean '경우' has 6 meanings, but we Korean use only two of them often. 경우 means 1.사리, 도리(synonym ):sense, duty, examples. I don't think that's sensible.:나는 그것이 경우에 맞다고 생각하지 않아. He is a reasonable man.:그는 경우가 밝은 사람이다. 2.상황,조건,형편,사정(synonym ) case, circumstances, scenario in my case:내 경우에는 in this case:이 경우에는 Use it for a special occasion.:특별한 경우에만 그것을 사용한다. Don't add dressing all at once in case you don't need it all. : 다 필요하지 않을 경우엔, dressing을 한꺼번에(all at once) 넣지 마세요(don't add). c.f.:경우(境遇) 【형편】circumstances;a situation; 【사례】a case;an instance; 【때】anoccasion;a time;a moment

In addition to Sujin Kim's answer: 경우 means a certain case where people behave/speak properly, a bit like a precedent for something(behavior, remark etc). For example, 이건 무슨 경우야? means "There's no case like this as far as I know, so I'd like an explanation" or "In what case would one do such a thing?". 이건 또 무슨 경우야? is more emphatic. Be aware that they're both informal. 그건 경우가 아니지. That's not the case (where one would do such a thing).

If someone asks you for directions, you would tell them the direction. If you find a lost purse on the street, you would report it to the police. These are the "case" I meant. If someone doesn't tell them the direction and report the lost purse to the police, you would say 경우 없다 or 경우가 아니다.

there will be some idiomatic expressions involving this word but usually it seems to correspond quite correctly to "case" in English (in such a case, in case of..., etc., or "if" in 비가 내릴 경우 "in case it rains/if it rains").