Because I'm - ~거든요

거든요 is used as a statement in which you give reasons / explanations for what you do or did.

• 하거든요 = Because (I) do

• 거든요 is a polite spoken form
• 거든 is a informal spoken form (however, if 거든 is used in the middle of a sentence (i.e. as a conjunction, linking two sentences), it means 'if')

For example,

• 벌써 왔어? = You came (back) already?
• 줄이 너무 길었거든. 그래서 그냥 왔어 = Because the queue was too long. So I just came (back).

• 줄이 너무 길거든, 그냥 와 = If the queue is too long, just come (back).

Take 다 off verbs/adjectives and add 거든요.

• 하다 → 하거든요 = Because (I) do
• 했다 → 했거든요 = Because (I) did
• 먹었거든요 = Because (I) ate
• 가거든요 = Because (I) go
• 갔거든요 = Because (I) went 
• 왔거든요 = Because (he) came
• 많았거든요 = Because (there) were many
• 배고팠거든요 = Because (I) was hungry
• 빠르거든요 = Because (it's) fast 
• 맛있거든요 = Because (it's) delicious

E.g.

• 아침 안 먹어요? = Don't you have breakfast?
• 네, 어제 저녁을 너무 많이 먹었거든요. = Yeah no, (because) I ate too much for dinner last night.

Note: 네 means 'yes.' 네 is used when you agree with the statement of the questioner.

• Don't you have breakfast? 네. (Yeah, I won't have breakfast)

Although in English, we say 'yes' to a negative question to mean a positive answer, 'no' is used in Korean to mean a positive answer (i.e. 'no' is used to mean a 'double negative' (= positive)). 

• Don't you have breakfast? Yes, I'll have breakfast (in English)
• Don't you have breakfast? 아뇨, 먹을 거에요 = No, I will have breakfast (in Korean)

아뇨 is a contracted form of 아니오 which means 'no.'

Example sentences

• 새 노트북 샀네요? = (Hey,) you bought a new laptop
• 네, 예전 노트북은 너무 느렸거든요. 그래서 새 노트북 샀어요 = Yeah, (because) the laptop I had before was too slow. So I bought a new laptop.

• 여기 레스토랑 음식이 진짜 맛있거든. 여기서 먹을래? = (Because) this restaurant's food is really delicious. Shall we eat here?
• 그래, 좋지. = Yeah, I'd like to.

• 피곤해 보여요 = You look tired
• 어제 잠을 많이 못잤거든요 = (Because) I didn't have much sleep last night.

• 되게 신나 보여요 = You look very excited!
• 예, 내일 홍콩으로 여행 가거든요 = Yeah, (because) I'm going on a trip to Hong Kong tomorrow!

새 (a simplified form of 새로운) = new

사다 = buy

샀다 = bought

샀네요 = (hey, you) bought

노트북 = laptop (literally, notebook)

느리다 = slow

느렸다 = was slow

그래 = ok, yeah

잠 = sleep (noun)

자다 = sleep (verb)

잤다 = slept 

피곤하다 = tired

피곤해 보이다 = look tired

되게 = very

신나다 = excited

홍콩 = Hong Kong

여행 가다 = go on a trip