TTMIK Level 5 Lesson 14 - -(으)니까, -(으)니

In this lesson, we take a look at the verb ending -(으)니까 [-(eu)ni-kka]. Through our previous lessons, we have introduced how to use 그래서 and -아/어/여서 to link sentences and show a reason/result relationship between them. This verb ending, -(으)니까, is used when the verb before -(으)니까 is the reason for another action or the basis of a judgement.

Construction
Verb #1 Stem + -(으)니까 + Verb #2

The verb (Verb #1) before -(으)니까 is the reason or the basis of judgement for Verb #2.

Difference between -아/어/여서 and -(으)니까
- Both of these structures show the reason/result or cause/effect relationship of two verbs, but -아/어/여서 can't be used in imperative sentences or with "Let's".

Ex)
지금 바쁘니까 나중에 전화해 주세요. (O)
= I am busy now so call me later.

지금 바빠서 나중에 전화해 주세요. (X)
** -아/어/여서 can't be used with imperative sentences.

Ex 2)
지금 피곤하니까 우리 영화 내일 봐요. (O)
= I am tired now so let's watch the movie tomorrow.

지금 피곤해서 우리 영화 내일 봐요. (X)
** -아/어/여서 can't be used with "Let's".
(우 리 영화 내일 봐요 can be translated in two ways. When 봐요 is translated as "let's watch", the entire sentence can NOT exist. But when 봐요 just means "we are watching" or "we are going to watch", the whole sentence can mean "We are tired now so we are going to watch the movie tomorrow.")

- For basic greetings and when talking about your own feelings or situations, you can’t use -(으)니까 and you have to use -아/어/여서.

Ex)
와 줘서 고마워요. (O)
= Thank you for coming.

와 주니까 고마워요. (X)

Ex 2)
어제 아파서 못 왔어요. (O)
= I was sick yesterday so I couldn't come.

어제 아프니까 못 왔어요. (X)

Sometimes, -(으)니까 can mark the end of the sentence when you are simply answering a question or providing a basis for a judgement or an action.

Ex)
Q. 이거 왜 샀어요? = Why did you buy this?
A. 맛있으니까. = Because it is delicious. (반말/casual language)
= 맛있으니까요. (존댓말/polite and formal language)

Ex)
괜찮아요. 아까 봤으니까.
= It is okay. (Because) I already saw it earlier.
** In this sentence, if you are speaking in 존댓말, you need to add -요 after 봤으니까 but it is still OKAY not to add it because this can be understood as a simple change of order of the sentence parts. (아까 봤으니까 괜찮아요 --> 괜찬아요, 아까 봤으니까.)

Sample sentences
1. 더우니까 에어컨 켤까요? = It's hot, so shall we turn on the airconditioner?

- 더워서 에어컨 켤까요? (X)

- 더워서 에어컨 켰어요. (O)
(= It was hot so I turned on the airconditioner.)

2. 저 지금 바쁘니까 나중에 전화해 주세요. = I am busy now so call me later.

- 저 지금 바빠서 나중에 전화해 주세요. (X)

- 저 지금 바쁘니까 나중에 전화할게요. (O)
(= I am busy now so I will call you later.)

3. 냉장고에 불고기 있으니까 먹어. = There is some bulgogi in the refrigerator so eat it.

- 냉장고에 불고기 있어서 먹어. (X)

- 냉장고에 불고기 있어서 먹었어요. (O)
(= There was some bugogi in the refrigerator so I ate it.)

4. 내일 일요일이니까 내일 하세요. = Tomorrow is Sunday so do it tomorrow.

- 내일 일요일이어서 내일 하세요. (X)

- 내일 일요일이어서 일 안 할 거예요. (O)
(= Tomorrow is Sunday so I am not going to work.)