A/V-거든(요) grammar = because ~respond to a question or statement to provide a reason or thinking

A/V-거든(요) grammar = because ~used to respond to a question or statement to provide the reason or thinking

Usage:
- A/V-거든(요) is used in sentence-final to respond to a question or statement in order to provide a reason or thinking. It  is only used in casual speaking between friends or peers = because

- A/V-거든 is used in mid-sentence to express a conditional statement in casual conversation

See: A/V-거든 grammar = if (something is true), then ~express condition in casual conversation

Tense:

Adjective/ Verb + -거든요 (Present tense) 

좋다 --> 좋거든요. 

있다 --> 있거든요. 

느리다  -->느리거든요. 

가다 --> 가거든요. 

먹다 --> 먹거든요. 

Adjective/ Verb +  -았/었거든요 (Past tense) 

좋다 --> 좋았거든요.

있다 --> 있었거든요. 

느리다  -->느렸거든요. 

가다 --> 갔거든요. 

먹다 --> 먹었거든요. 

Adjective/ Verb + -(으)ㄹ 거든요 (Future tense)

좋다 --> 좋을 거든요.

있다 --> 있을 거든요.

느리다  --> 느릴 거든요.

가다 -->  갈 거든요.

먹다 -->  먹을 거든요.

Noun + (이)거든요 (Present tense) / 였거든요 (Past tense)

학생 --> 학생이거든요. 

장마철 --> 장마철이거든요.

일요일 --> 일요일이거든요.

회의 중 --> 회의 중이거든요.

Examples:

1. 가방이 무거워 보이는데 도와줄까요?

- 괜찮아요. 무거워 보이지만 가볍건든요.

My bag looks heavy, can I help you?

- It's okay. It looks heavy, but it's light.

2. 오늘 왜 그렇게 피곤해 보여요?
- 어제 영화를 보느라고 잠을 못 잤거든요.

Why do you looked so tired today?
-  I couldn’t sleep well since I watched a movie yesterday.

3. 제주도에 갔을 때 한라산에 올라갔어요?
- 아니요, 못 갔어요. 날씨가 안 좋았거든요.

Did you go up Halla mountain when you went to Jeju?
- No, I didn't because the weather was bad.

4. 요즘 비가 정말 자주 오네요.
- 요즘 장마철이거든요. 한 달 동안 계속 올 거예요.

It’s has been raining a lot recently.
- Since it is currently the rainy season. It will rain for a month.

5. 공항에 무슨 일로 가세요?
- 오늘 부모님이 한국에 오시거든요.

How come do you go to the airport?
- Because today my parents come to Korea.

6. 주말에 그 드라마를 보셨어요?
- 아니요, 못 봤어요. 친구랑 약속이 있었거든요.

Did you watch that drama in weekend?
- No, I couldn't. Because I have an appointment with my friend.

7. 왜 음식을 이렇게 많이 준비해요?
- 집에 친구들이 많이 오거든요.

Why do you prepare this much food?
- Because many of my friends will come to my house.

8. 새 노트북을 샀네요?
- 네, 예전 노트북은 너무 느렸거든요. 그래서 새 노트북을 샀어요.

Did you buy a new notebook?
- Yes, the previous one is very slow. So I bought a new one.

9. 되게 신나 보여요?
- 예, 내일 프랑스로 여행 가거든요.

You look so excited.
- Yes, since I will go for traveling to France tomorrow.

10. 왜 점심을 안 먹었어요?
- 아침을 너무 많이 먹었거든요.

Why didn't you eat lunch?
- Because I ate too much in the morning.

11. 왜 서울에 가세요?

- 오늘 서울에서 중요한 회의 있거든요.

Why are you going to Seoul?

- Because I have an important meeting in Seoul today.

12. 커피 한 잔 드릴까요?

- 괜찮아요. 조금 전에 마셨거든요.

Do you want some coffee?

- It's okay. I've drank it a while ago.

13. 왜 기분이 안 좋아?

- 시험을 잘 못봤거든.

Why are you in a bad mood?

- Because I didn't do well on the exam. 

14. 사람들이 요즘 이 영화를 많이 보네요.

- 영화가 재미있거든요.

People are watching this movie a lot these days.

- Because the movie is interesting.

15. 안나 씨는 친구가 많네요.

- 성격이 사교적이거든요.

Anna has many friends.

- Because he personality is sociable.

16. 떡볶이를 왜 안 먹어요?

- 저는 매운 음식을 먹으면 배가 아프거든요.

Why don't you eat tteokbokki?

- Because my stomach hurts when I eat spicy food.

17. 토니 씨, 지금 통화할 수 있어요?

- 미안해요. 지금은 회의중이거든요. 제가 이따가 전화할게요.

Tony, can I speak to you now?

- Sorry. I'm in a meeting right now. I'll call you later.

18. 두통약 좀 주실래요? 머리가 너무 아프거든요.

Can I have me some headache pills? My head hurts so much.

19. 기사님, 조금 빨리 가 주시겠어요? 약속 시간에 늦었거든요.

 Mister, can you go a little faster? I'm late for my appointment.

20. 햄버거에서 양파는 빼 주세요. 제가 양파를 못 먹거든요.

Please remove the onion from the hamburger. Because I can't eat onions.

Specific usage:

1. When indicating a reason,  -거든요 must come either after an initial statement made by the speaker or in response to a question asked by a listener.

좋아하는 음악 밴드 있어요? 

- 노래를 잘하거든요. 소녀시대를 좋아해요. (Wrong)

- 노래를 잘해서 소녀시대 좋아해요. (Correct)

Is there any music band you like?

- I like Girls' generation because they sing well.

뭐 먹을까요?

- 냉면이 어때요? 이 식당은 냉면이 유명하거든요.

What shall we eat?

- How about cold noodle? Because this restaurant is famous for its cold noodles.

2. Provide a hint to the listener that the speaker has more to say.

죄송한데요. 이 근처에 은행이 어디에 있어요? 

- 이 길로 쯕 가시면 편의점이 나오거든요. 편의점 건너편에 은행이 있어요.

Excuse me, do you know if there is a bank nearby? 

- If you go straight on this road, you will see a convenience store. There is a bank across from the convenience store.

3. Difference between -거든요 and -니까요 grammars

They can be used interchangeably at some extent. However, their usage is different as below:

- 거든요 = because ~imply personal preference that only speaker knows

- 니까요 = because ~explain a cause and effect 

안나 씨는 저 식당에 자주 가는 것 같아요.

- 네. 가격이 싸고 음식이 맛있거든요. / 맛있니까요. 

Anna seems to go to that restaurant often.

- Yes. The price is cheap and the food is delicious.