A/V + 거든 [1] - if
Similar with : 거들랑, (으)면
Connective ending that shows a condition or a supposition. The second sentence is usually followed by an imperative sentence or a future sentence (-겠어요, -을 것이다). Even though (으)면 can be used with -을 수 있다, 거든 cannot be used with it.
친구를 만나거든 안부를 전해 주세요.
If you meet your friend send my regards
옷이 안 맞거든 언제든지 바꾸러 오세요.
If the clothes don't fit, come anytime to change them.
이번 시험을 잘 보거든 명문 대학교에 입학할 수 있어요. (X)
이번 시험을 잘 보면 명문 대학교에 입학할 수 있어요. (O)
If you do well on this exam, you will be able to get into a prestigious university.
A/V+ 거든(요) [2]
N+(이)거든(요)
A/V+았/었거든(요)
Similar with : 거들랑
An ending that shows the reason about something.
직장 동료들이 그를 싫어해. 술버릇이 나쁘거든.
His co-workers hate him. (Because) He has a nasty drinking habit.
It can also be used when "connecting" our story, thus adding more info on something we said.
요즘 내가 좋아하는 사람이 있거든. 그런데 그 사람은 내 마음을 몰라.
There is someone I like. But he doesn't know my feelings.
내가 좀 바쁘거든..그래서 나를 만날 수 없어.
I'm a little busy.. so I can't meet you.
Also used to express someone's understanding of something strange or weird.
귀신이 곡할 노릇이거든!
How very strange!
Some examples with -거든 at the end of a sentence, being used as "because".
그 일을 왜 좋아하느냐 하면 재미있거든요.
If I was to say why I like this jod, it's because it's fun.
그 남자 배우가 요즘 무척 인기가 있어요. 잘생겼거든요.
This actor is really popular these days. It's because he's handsome.
resource: 외국인을 위한 한국어 문법2
