안녕하세요! Today, we’re going to dive into an essential element of Korean grammar: 으니까 (because / since), written as -(으)니까. This versatile connector helps link clauses and express reasoning or causation. It’s part of the “because” cluster — compare it to 기 때문에 and 아/어서 to understand the key differences! 😊
In this lesson, we’ll explore the meaning of “-(으)니까”, how to use it in forming sentences, and its various applications in different contexts. We’ll also provide plenty of examples and practice exercises to help you master this structure. Let’s get started and unfold the wonders of “-(으)니까” together!
Conjugation
VERB + -(으)니까
- Take a verb i.e. 가다
- Drop “다” i.e. 가
- Add the appropriate verb ending based on the below rules (in this case it becomes “가니까”.
- If the verb stem ends in a vowel add “니까”
- If the verb stem ends in a consonant add “으니까”
- If the verb stem ends in a consonant “ㄹ”, drop “ㄹ” and add “니까”
- 보다 –> 보 + 니까 –> 보니까 (Since (someone) sees)
- 먹다 –> 먹 + 으니까 –> 먹으니까 (Since (someone) eats)
- 오다 –> 오 + 니까 –> 오니까 (Since (someone) comes)
- 하다 –> 하 + 니까 –> 하니까 (Since (someone) does)
Understanding -(으)니까
In the Korean language, “-(으)니까” is a connector that is commonly used to link clauses. It serves two main functions: to express a reason or cause, and to signal the listener that important information will follow.
The first usage of “-(으)니까”, to denote a reason or cause, is perhaps the most common. It is equivalent to the English “because” or “since.” For instance, in the sentence “비가 오니까 우산을 가져가요.” (Because it’s raining, take an umbrella.), “-(으)니까” links the cause (it’s raining) with the effect (taking an umbrella).
The second usage of “-(으)니까” is to signal that the speaker is about to provide important information or advice. In this case, the structure doesn’t necessarily indicate a cause-effect relationship. For example, “잘 들어, 내가 할 말이 있으니까요.” (Listen carefully, because I have something to say.) Here, “-(으)니까” is used to emphasize that the speaker is about to say something significant.
Understanding the nuances of “-(으)니까” and its functions will allow you to create complex sentences and express your thoughts more effectively in Korean. Next, let’s delve into how we can form sentences using “-(으)니까”.
Forming sentences
Forming sentences with “-(으)니까” is quite straightforward once you understand the rules. Let’s start with the basic structure. The “-(으)니까” form is attached directly to the verb or adjective stem, but the form it takes depends on whether the stem’s final syllable ends in a vowel or a consonant.
If the stem ends in a vowel, you add “-니까”. For instance, the verb 먹다 (to eat) becomes 먹으니까, and 가다 (to go) becomes 가니까.
If the stem ends in a consonant, you add “-으니까”. For example, the verb 읽다 (to read) becomes 읽으니까, and the adjective 좋다 (to be good) becomes 좋으니까.
This rule also applies when the verb or adjective stem ends in ‘ㄹ’, even though ‘ㄹ’ is technically a consonant. So, for example, the verb 날다 (to fly) becomes 나니까, not *날으니까.
Note that “-(으)니까” can be used with both action verbs and descriptive verbs (adjectives), making it a very versatile connector. So, you could say “배가 고프니까 먹어야 해” (Because I’m hungry, I have to eat), linking an adjective (hungry) with an action (eat).
Now that we’ve understood how to form sentences with “-(으)니까”, let’s move on to practical examples in various contexts to help solidify your understanding.
Examples
Now, let’s put the theory into practice and dive into some examples of how to use “-(으)니까” in a sentence.
- 늦으니까 빨리 가요. (Because it’s late, let’s go quickly.) In this sentence, “-(으)니까” is used to express the reason for needing to go quickly. The verb 늦다 (to be late) is turned into 늦으니까 to express the cause or reason.
- 많이 배우니까 자신감이 생겨요. (Because I am learning a lot, I am gaining confidence.) Here, the verb 배우다 (to learn) is converted into 배우니까 to link the cause (learning a lot) with the effect (gaining confidence).
- 피곤하니까 일찍 잘게요. (Because I’m tired, I’ll go to bed early.) In this case, the adjective 피곤하다 (to be tired) is changed into 피곤하니까 to indicate the reason for going to bed early.
- 그 사람이 도와주니까 일이 잘 풀려요. (Because that person is helping me, the work is going well.) The verb 돕다 (to help) is turned into 도와주니까 to denote the reason why the work is going well.
- 비가 오니까 우산을 가져가세요. (Because it’s raining, take an umbrella.) The verb 오다 (to come/rain) is used here as 오니까 to show the cause for needing to take an umbrella.
- 중요한 일이 있으니까 말을 들어봐요. (Because there’s something important, listen to what I say.) In this example, the expression 있으니까 is used to signal that important information will follow.
These examples should give you a practical sense of how “-(으)니까” can be used in everyday Korean. Remember, the key to mastering any language structure is through practice. Therefore, try to form your own sentences using “-(으)니까” to reinforce your understanding.
Past tense
Forming past tense sentences with “-(으)니까” is straightforward once you understand the conjugation rule for past tense verbs and adjectives in Korean.
If the stem ends in a vowel, you would add -았/었 after the stem to indicate the past tense, and then add 으니까 because it will always end in the consonant “ㅆ”.
For instance, the verb 먹다 (to eat) in past tense becomes 먹었으니까 (because I ate), and 가다 (to go) becomes 갔으니까 (because I went).
Similarly, the adjective 좋다 (to be good) in past tense becomes 좋았으니까 (because it was good), and the verb 읽다 (to read) becomes 읽었으니까 (because I read).
Remember, the purpose of “-(으)니까” is to provide a reason or cause for something, so it often precedes a result or an effect.
For example:
- 책을 읽었으니까 시험에 합격했어요. (Because I read the book, I passed the exam.)
- 비가 왔으니까 우산을 썼어요. (Because it rained, I used an umbrella.)
- 친구가 도와줬으니까 숙제를 빨리 끝냈어요. (Because my friend helped me, I finished my homework quickly.)
Future tense
Creating future tense sentences with “-(으)니까” in Korean is also following similar rules.
To form future tense sentences, you would add “-ㄹ/을 거”to the stem of the verb or adjective, then append -니까.
For instance, 가다 (to go) becomes 갈 거니까 (Since I will be going), and the verb 보다 (to see) becomes 볼 거니까 (Since I am going to see).
Let’s consider some examples:
- 내일 비가 올 거니까 우산을 챙기세요. (Since it will rain tomorrow, take an umbrella.)
- 내일 도와줄 거니까 오늘은 그냥 쉬어요. (Since I will help you tomorrow, just take a rest today.)
- 다음 주는 엄마가 올 거이까 선물 사요. (Since mom will come next week, buy a present.)
As these examples illustrate, the usage of -니까 in the future tense doesn’t always imply direct causation, but more of an expectation or anticipation based on certain future conditions or plans. Practice forming your own sentences with “-(으)니까” in the future tense to familiarize yourself with this usage. For other ways to express “because” or “since” in Korean, see our lessons on 기 때문에 and 아/어서.
Activity 1
Fill in the blanks
- 기분이 _________ 노래를 불렀어요. – I sang because I was in a good mood.
- 배가 _______ 저녁을 일찍 먹어요. – Since I am hungry I am eating dinner early.
- 시간이 ________ 택시를 탔어요. – I took a taxi because I didn’t have time.
- _________ 자켓을 입었어요. – I wore a jacket because it was cold.
- 내일 날씨가 ________ 같이 산책 해요. – Since the weather will be nice tomorrow, let’s go for a walk together.
Activity 1 Answers
- 기분이 좋았으니까 노래를 불렀어요. – I sang because I was in a good mood.
- 배가 고프니까 저녁을 일찍 먹어요. – Since I am hungry I am eating dinner early.
- 시간이 없었으니까 택시를 탔어요. – I took a taxi because I didn’t have time.
- 추웠으니까 자켓을 입었어요. – I wore a jacket because it was cold.
- 내일 날씨가 좋을 거니까 같이 산책 해요. – Since the weather will be nice tomorrow, let’s go for a walk together.
(으)니까 vs 아서/어서 vs 기 때문에: The Complete Comparison
This is the question I get asked most about Korean “because” structures — when do you use which one? I struggled with this for a long time, so here’s the clearest breakdown I can give you:
| (으)니까 | 아서/어서 | 기 때문에 | |
|---|---|---|---|
| Meaning | because / since | because / so (sequential) | because of / due to |
| Formality | Polite/formal — works at all levels | Conversational — polite speech | More formal/written |
| After commands/requests? | ✅ YES — can precede commands | ❌ NO — cannot precede commands | ✅ YES — can precede commands |
| Tense in first clause? | ✅ Can use past/future tense | ❌ Only present stem (no past/future) | ✅ Can use any tense |
| Emphasis | Speaker’s subjective reason/judgement | Logical sequence / cause | Objective fact/reason |
| Example | 비가 오니까 우산 가져가세요. | 비가 와서 우산을 샀어요. | 비가 오기 때문에 못 나갔어요. |
💡 The most important rule to remember: Only (으)니까 can come before commands (-(으)세요), suggestions (-(으)ㄹ까요), and requests. 아서/어서 cannot. This is the rule that trips up learners most often — and it’s also the one I kept getting marked wrong on before I properly memorised it!
Commands — only (으)니까 works
- ✅ 늦었으니까 빨리 가세요. — Because it’s late, please go quickly.
- ❌ 늦었어서 빨리 가세요. — ✗ (Incorrect — 아서/어서 cannot precede a command)
Sequential cause — 아서/어서 feels more natural
- 배가 고파서 밥을 먹었어요. — I was hungry, so I ate. (natural sequence)
- 배가 고프니까 밥을 먹었어요. — Because I was hungry, I ate. (more emphatic / explaining)
Past tense in the first clause — (으)니까 only
- ✅ 어제 많이 먹었으니까 오늘은 조금만 먹어요. — Because I ate a lot yesterday, I’ll eat just a little today.
- ❌ 어제 많이 먹었어서 오늘은 조금만 먹어요. — ✗ (Incorrect — 어서 cannot take past tense)
The One Rule You Must Know: (으)니까 Before Commands
If there is one thing to burn into your memory about (으)니까, it’s this: when the second clause is a command, request, or suggestion, you must use (으)니까 — not 아서/어서.
This comes up constantly in real Korean — giving directions, making suggestions, giving advice:
- 날씨가 좋으니까 같이 산책해요! — The weather is nice, so let’s take a walk!
- 시험이 있으니까 열심히 공부하세요. — Since there’s an exam, please study hard.
- 피곤하니까 좀 쉬세요. — Since you’re tired, please rest a bit.
- 맛있으니까 한 번 먹어 보세요. — Because it’s delicious, try eating it.
- 시간이 없으니까 빨리 결정해요. — Since there’s no time, decide quickly.
In everyday Korean life I heard this pattern constantly — especially from shop owners, teachers, and older Koreans giving advice. Once you recognise it, you’ll hear it everywhere.
(으)니까 in Real Conversations
Here’s how (으)니까 sounds in natural, everyday Korean across different situations:
Making excuses (very useful!)
- 바쁘니까 나중에 얘기해요. — I’m busy, so let’s talk later.
- 돈이 없으니까 못 사요. — I don’t have money, so I can’t buy it.
- 한국어를 잘 못하니까 천천히 말해 주세요. — Since I can’t speak Korean well, please speak slowly.
Giving advice or suggestions
- 감기에 걸렸으니까 오늘은 집에 있어요. — Since you caught a cold, stay home today.
- 내일 일찍 출발해야 하니까 오늘 일찍 자세요. — Since you have to leave early tomorrow, go to bed early today.
- 한국어 실력이 좋아졌으니까 이제 드라마 자막 없이 봐요. — Since your Korean has improved, now watch dramas without subtitles!
Explaining a decision
- 한국을 좋아하니까 한국어를 배우기 시작했어요. — Because I love Korea, I started learning Korean.
- K-드라마가 재미있으니까 매일 봐요. — Since K-dramas are interesting, I watch them every day.
- 서울에 가봤으니까 부산도 가보고 싶어요. — Since I’ve been to Seoul, I want to visit Busan too.
(으)니까 Conjugation Quick Reference
A quick reminder of all the conjugation rules in one place:
| Verb stem ends in | Rule | Example | Result |
|---|---|---|---|
| Vowel | Add 니까 | 가다 → 가 | 가니까 |
| Consonant | Add 으니까 | 먹다 → 먹 | 먹으니까 |
| ㄹ (irregular) | Drop ㄹ, add 니까 | 알다 → 아 | 아니까 |
| Past tense stem | Always add 으니까 (ends in ㅆ) | 먹었다 → 먹었 | 먹었으니까 |
| Future tense | Add -(으)ㄹ 거니까 | 가다 → 갈 거 | 갈 거니까 |
Practice: More Exercises
Exercise 2: Choose the correct connector
For each sentence, decide whether (으)니까 or 아서/어서 fits better (or which one is grammatically required):
- 날씨가 추우_____ 따뜻하게 입으세요. (The weather is cold so please dress warmly.)
- 배가 고파_____ 밥을 먹었어요. (I was hungry so I ate.)
- 비가 왔_____ 우산을 썼어요. (It rained so I used an umbrella.)
- 시간이 없_____ 택시를 타세요. (There’s no time, so take a taxi.)
- 친구를 만나_____ 기분이 좋아요. (I met a friend and feel good.)
Answers:
- 추우니까 — command follows (입으세요), so must use (으)니까
- 고파서 — natural sequence, no command, 아서/어서 works well but also 으니까
- 왔으니까 — past tense in first clause, only (으)니까 works
- 없으니까 — command follows (타세요), so must use (으)니까
- 만나서 — sequential cause, no command, 아서/어서 works naturally
Exercise 3: Translate to Korean using (으)니까
- Because it’s cold, please close the window. (춥다 + 창문 닫다)
- Since I studied hard, I passed the exam. (열심히 공부하다 + 시험에 합격하다)
- Because Korean is fun, I study every day. (재미있다 + 매일 공부하다)
- Since it will rain tomorrow, bring an umbrella. (비가 오다 + 우산 가져오다)
Answers:
- 추우니까 창문 닫으세요.
- 열심히 공부했으니까 시험에 합격했어요.
- 한국어가 재미있으니까 매일 공부해요.
- 내일 비가 올 거니까 우산 가져오세요.