If you want to make some friends to help you with your Korean, this word is of course, very important. The word friend can be used in many situations here, but one thing I was confused about when I first arrived, is that you can’t use it for everyone, even if you would be considered friends back in your home country.
In Korea, there is a very strict hierarchy system which is very evident in the language. For instance, very rarely will you call someone, even family members or coworkers by their name. Everyone has titles. The same goes for friend. Let’s explain further:
This is the word that directly translates into ‘friend’ in English. However, you can only use this terms for people you are close to who are the same age as you (born in the same year). Anyone born in the same year can be considered your friend.
These words refer to someone older than you who you are very close to. Basically a friend, but because of the hierarchy, you would use a formal term to refer to them. 형 is used by younger men to refer to a male friend older than them. 언니 is used by younger women to refer to a female friend older than them. In a family sense, these are also used to refer to brother and sister in the same manner.
These also refer to someone older. 오빠 is used by younger women to refer to an older man they consider a friend (also used by women as a way to call their boyfriends/husbands). 누나 is used by younger men to refer to an older woman they consider a friend.
Other words that contain 친구:
여자친구/여친 (yeo-ja-chin-gu/yeo-chin) = Girlfriend
남자친구/남친 (nam-ja-chin-gu/nam-chiin) = Boyfriend
As you can see, it can be a little confusing at first. Most learners are used to using just one word for friend. But it quickly gets easier and you will remember them quickly if you can consistently studying Korean. it basically becomes second nature.