-(으)니까 expresses reason or cause with emphasis. It means "since," "because," or "so" and can be used with commands and suggestions.
Structure
Clause 1 + -(으)니까, Clause 2
Breakdown:
- -(으)니: Causal connective
- 까: Emphasizing ending
Meaning: "Since [clause 1], [clause 2]" or "Because [clause 1], [clause 2]"
Conjugation Rules
After Vowel or ㄹ: -니까
No final consonant:
- 가다 → 가니까 (since/because go)
- 오다 → 오니까 (since/because come)
- 하다 → 하니까 (since/because do)
After ㄹ (drop ㄹ):
- 만들다 → 만드니까 (since/because make)
- 팔다 → 파니까 (since/because sell)
After Consonant: -으니까
Final consonant present:
- 먹다 → 먹으니까 (since/because eat)
- 읽다 → 읽으니까 (since/because read)
- 앉다 → 앉으니까 (since/because sit)
- 좋다 → 좋으니까 (since/because good)
Core Differences from -아/어서
Can Use with Commands
✓ -(으)니까 allows:
- 바쁘니까 가세요 (You're busy, so please go)
- 피곤하니까 쉬세요 (You're tired, so please rest)
- 추우니까 문 닫으세요 (It's cold, so please close the door)
✗ -아/어서 cannot:
- 바빠서 가세요 ✗
Can Use with Suggestions
✓ -(으)니까 allows:
- 늦었으니까 택시 탑시다 (It's late, so let's take a taxi)
- 비오니까 우산 가져갑시다 (It's raining, so let's take an umbrella)
✗ -아/어서 cannot:
- 늦어서 택시 탑시다 ✗
Stronger Causation
-(으)니까: Emphasizes cause-effect
- 비가 오니까 취소했어요 (BECAUSE it rained, we cancelled)
- → Stronger, more definitive
-아/어서: Natural reason
- 비가 와서 취소했어요 (It rained, so we cancelled)
- → Softer, more neutral
Common Usage Patterns
Giving Commands Based on Reason
Imperative after reason:
- 위험하니까 조심하세요 (It's dangerous, so be careful)
- 시간 없으니까 빨리 가세요 (There's no time, so please go quickly)
- 중요하니까 확인하세요 (It's important, so please check)
- 좋은 기회니까 하세요 (It's a good opportunity, so do it)
Making Suggestions
Proposals based on reasons:
- 날씨 좋으니까 산책할까요? (The weather's nice, so shall we take a walk?)
- 시간 있으니까 천천히 합시다 (We have time, so let's do it slowly)
- 배고프니까 밥 먹읍시다 (We're hungry, so let's eat)
Explaining Discoveries
Realizing something:
- 봤더니 재미있네요 (I watched it and it's interesting)
- 들었더니 좋네요 (I listened and it's good)
- 해 봤더니 쉽네요 (I tried it and it's easy)
With Adjectives
State Causing Action
Adjective + -(으)니까:
- 좋으니까 사세요 (It's good, so buy it)
- 싸니까 많이 사세요 (It's cheap, so buy a lot)
- 비싸니까 생각해 보세요 (It's expensive, so think about it)
- 쉬우니까 혼자 해 보세요 (It's easy, so try it alone)
Discovering Reasons
Realizing Through Experience
Pattern: [Action]-(으)니까 [Discovery]
Examples:
- 와 보니까 좋네요 (Now that I've come, it's nice)
- 먹어 보니까 맛있네요 (Now that I've tried it, it's delicious)
- 해 보니까 어렵네요 (Now that I've done it, it's difficult)
- 들어 보니까 이상하네요 (Now that I've heard it, it's strange)
Meaning: "Now that..." / "Having done..."
Tense Usage
Past Tense: -았/었으니까
Past reason for current action:
- 다 먹었으니까 가도 돼요 (I've finished eating, so we can go)
- 준비했으니까 시작합시다 (We've prepared, so let's start)
- 약속했으니까 꼭 가야 해요 (We promised, so we must go)
Present Tense: -(으)니까
Current state as reason:
- 늦었으니까 빨리 가요 (It's late, so let's go quickly)
- 비오니까 우산 가져가세요 (It's raining, so take an umbrella)
Negative Forms
With 안 (Not)
Negative reason:
- 안 좋으니까 버리세요 (It's not good, so throw it away)
- 안 바쁘니까 천천히 해요 (I'm not busy, so take your time)
- 안 비싸니까 사세요 (It's not expensive, so buy it)
With -지 않으니까
Formal negative:
- 좋지 않으니까 하지 마세요 (It's not good, so don't do it)
- 맞지 않으니까 바꾸세요 (It doesn't fit, so change it)
With Questions
Asking Why
Pattern: Why question + -(으)니까 answer
A: 왜 안 왔어요? (Why didn't you come?) B: 아팠으니까요 (Because I was sick)
Note: -(으)니까요 can stand alone as answer
Contrast: -(으)니까 vs -아/어서
Key Differences
| Feature | -(으)니까 | -아/어서 |
|---|---|---|
| With commands | ✓ Can use | ✗ Cannot |
| With suggestions | ✓ Can use | ✗ Cannot |
| With future | ✓ Can use | ✗ Cannot |
| Causation strength | Stronger | Softer |
| Formality | More formal | More casual |
| Discovery | ✓ "Now that" | ✗ Not used |
Examples Compared
With Command:
- ✓ 춥으니까 문 닫으세요 (It's cold, so close the door)
- ✗ 추워서 문 닫으세요
With Suggestion:
- ✓ 비오니까 집에 있을까요? (It's raining, shall we stay home?)
- ✗ 비와서 집에 있을까요?
Neutral Statement:
- ✓ 비오니까 못 갔어요 (It rained, so I couldn't go)
- ✓ 비와서 못 갔어요 (It rained, so I couldn't go)
- → Both work, -(으)니까 stronger
Example Dialogues
Dialogue 1: Giving Advice
A: 오늘 뭐 입을까요?
(What should I wear today?)
B: 춥으니까 따뜻하게 입으세요.
(It's cold, so dress warmly.)
Dialogue 2: Making Plans
A: 날씨가 좋네요.
(The weather is nice.)
B: 그러니까 밖에 나갑시다.
(That's why let's go outside.)
Dialogue 3: Discovery
A: 이 식당 어때요?
(How is this restaurant?)
B: 와 보니까 정말 좋네요!
(Now that I've come, it's really good!)
Dialogue 4: Warning
A: 여기 가도 돼요?
(Can I go here?)
B: 위험하니까 가지 마세요.
(It's dangerous, so don't go.)
Common Expressions
Giving Reasons for Commands
- 위험하니까 조심하세요 (It's dangerous, so be careful)
- 중요하니까 잘 들으세요 (It's important, so listen well)
- 어려우니까 천천히 하세요 (It's difficult, so do it slowly)
- 늦었으니까 빨리 가세요 (It's late, so go quickly)
Making Decisions
- 시간 없으니까 택시 탑시다 (We don't have time, so let's take a taxi)
- 비싸니까 사지 맙시다 (It's expensive, so let's not buy it)
- 좋으니까 해 봅시다 (It's good, so let's try it)
Explaining Through Experience
- 해 보니까 쉽네요 (Having done it, it's easy)
- 와 보니까 멀지 않네요 (Having come, it's not far)
- 먹어 보니까 맛있네요 (Having tasted it, it's delicious)
Common Mistakes
❌ Incorrect: 가니까서
Mixing forms
✅ Correct: 가니까
Just -(으)니까
❌ Incorrect: 바빠서 가세요
Using -아/어서 with command
✅ Correct: 바쁘니까 가세요
Use -(으)니까 for commands
❌ Incorrect: 갔으니까
Wrong past tense formation
✅ Correct: 갔으니까 (if verb) or 가니까 (if adjective state)
Check if action or state
Special Usage: -았/었더니
Discovery Through Experience
Pattern: -았/었더니
Similar to -(으)니까 but past discovery:
- 먹어 봤더니 맛있네요 (I tried it and it's delicious)
- 가 봤더니 멀지 않네요 (I went and it's not far)
- 들었더니 좋네요 (I heard it and it's good)
Summary Table
| Usage | -(으)니까 | -아/어서 |
|---|---|---|
| Simple reason | ✓ | ✓ (softer) |
| With command | ✓ | ✗ |
| With suggestion | ✓ | ✗ |
| Discovery | ✓ | ✗ |
| Stronger causation | ✓ | - |
| More formal | ✓ | - |
Key Takeaways
✅ Strong causation: Emphasizes cause-effect relationship
✅ After vowel/ㄹ: -니까
✅ After consonant: -으니까
✅ Can use with commands: Unlike -아/어서
✅ Can use with suggestions: -(으)ㅂ시다, -(으)ㄹ까요?
✅ Discovery meaning: "Now that..." / "Having..."
✅ More formal: Than -아/어서
-(으)니까 is essential for expressing reasons in Korean, especially when giving commands, making suggestions, or emphasizing causation. While -아/어서 is softer and more neutral, -(으)니까 is stronger and more versatile, working in contexts where -아/어서 cannot.