Overview
~(으)니까 is a powerful connector that means "because" or "since." It shares some territory with ~아/어서 but has unique abilities:
- Can be used with commands and suggestions (unlike ~아/어서)
- Can take past tense on the first clause (unlike ~아/어서)
- Can express discovery -- finding something out upon doing something
- Has a stronger, more assertive tone than ~아/어서
How to Form ~(으)니까
| Stem ending | Ending | Example |
|---|---|---|
| Vowel (no 받침) | ~니까 | 가다 → 가니까, 비싸다 → 비싸니까 |
| Consonant (받침) | ~으니까 | 먹다 → 먹으니까, 없다 → 없으니까 |
| ㄹ받침 | ~니까 (drop ㄹ? No -- keep ㄹ) | 알다 → 아니까, 멀다 → 머니까 |
Wait -- ㄹ behaves specially. When a suffix starting with ㄴ, ㅂ, or ㅅ follows ㄹ, the ㄹ drops:
| Dictionary | Stem | + (으)니까 | Result |
|---|---|---|---|
| 가다 | 가 | 가 + 니까 | 가니까 |
| 오다 | 오 | 오 + 니까 | 오니까 |
| 먹다 | 먹 | 먹 + 으니까 | 먹으니까 |
| 읽다 | 읽 | 읽 + 으니까 | 읽으니까 |
| 없다 | 없 | 없 + 으니까 | 없으니까 |
| 있다 | 있 | 있 + 으니까 | 있으니까 |
| 좋다 | 좋 | 좋 + 으니까 | 좋으니까 |
| 알다 | 알 | 아 + 니까 | 아니까 (ㄹ drops) |
| 멀다 | 멀 | 머 + 니까 | 머니까 (ㄹ drops) |
| 살다 | 살 | 사 + 니까 | 사니까 (ㄹ drops) |
| 하다 | 하 | 하 + 니까 | 하니까 |
With past tense
~(으)니까 allows past tense on the first clause. Add ~았/었 before ~으니까:
| Dictionary | Past + 으니까 | Result |
|---|---|---|
| 가다 | 갔 + 으니까 | 갔으니까 |
| 먹다 | 먹었 + 으니까 | 먹었으니까 |
| 하다 | 했 + 으니까 | 했으니까 |
| 없다 | 없었 + 으니까 | 없었으니까 |
Part 1: Reason with Commands and Suggestions
The primary advantage of ~(으)니까 over ~아/어서 is that it works with commands and suggestions.
With commands (~세요, ~(으)십시오)
- 추우니까 옷을 입으세요. (It's cold, so please put on clothes.)
- 위험하니까 조심하세요. (It's dangerous, so please be careful.)
- 시간이 없으니까 빨리 하세요. (There's no time, so please hurry.)
- 비가 오니까 우산 가져가세요. (It's raining, so take an umbrella.)
With suggestions (~자, ~(으)ㅂ시다)
- 배고프니까 밥 먹자. (I'm hungry, so let's eat.)
- 날씨가 좋으니까 산책합시다. (The weather is nice, so let's take a walk.)
- 시간이 있으니까 영화 보자. (We have time, so let's watch a movie.)
- 늦었으니까 택시 탑시다. (We're late, so let's take a taxi.)
Compare with ~아/어서
| ~아/어서 (X with commands) | ~(으)니까 (O with commands) |
|---|---|
| 추워서 옷 입으세요 (X) | 추우니까 옷 입으세요 (O) |
| 배고파서 먹자 (X) | 배고프니까 먹자 (O) |
| 늦어서 빨리 갑시다 (X) | 늦었으니까 빨리 갑시다 (O) |
Part 2: Discovery / Realization
~(으)니까 can express that you discovered or realized something upon doing an action. This is a meaning that ~아/어서 does not have.
- 가 보니까 아무도 없었어요. (When I went and looked, nobody was there.)
- 먹어 보니까 맛있었어요. (When I tried eating it, it was delicious.)
- 해 보니까 어렵지 않았어요. (When I tried doing it, it wasn't difficult.)
- 만나 보니까 좋은 사람이었어요. (When I met them, they were a nice person.)
This pattern often combines with ~아/어 보다 (to try doing):
Verb stem + 아/어 보니까 = "When I tried [verb]-ing, (I found that)..."
Part 3: Strong Emphasis on Reason
~(으)니까 carries a more assertive, emphatic tone than ~아/어서. It is often used when the speaker wants to strongly justify or persuade.
- 제가 했으니까 걱정하지 마세요. (I did it, so don't worry.)
- 내가 할 거니까 신경 쓰지 마. (I'll do it, so don't bother.)
- 벌써 끝났으니까 됐어요. (It's already over, so that's enough.)
In spoken Korean, ~(으)니까 is sometimes shortened to ~(으)니까 → ~(으)니:
- 가니 (because I go)
- 먹었으니 (because I ate)
And in very casual speech, it can become ~(으)니깐 or ~(으)니:
- 추우니깐 들어가자. (It's cold so let's go in.)
~(으)니까 vs. ~아/어서: Complete Comparison
| Feature | ~아/어서 | ~(으)니까 |
|---|---|---|
| Statements | O | O |
| Questions | O | O |
| Commands (~세요) | X | O |
| Suggestions (~자) | X | O |
| Past tense on 1st clause | X | O |
| Discovery meaning | X | O |
| Tone | Soft, natural | Strong, assertive |
| Common in | Conversational reasons | Persuading, justifying |
When to choose which
- Giving a soft reason: ~아/어서
-
피곤해서 일찍 잤어요. (I was tired so I slept early.)
-
Giving a reason with a command or suggestion: ~(으)니까
-
피곤하니까 일찍 자세요. (You're tired, so sleep early.)
-
Expressing discovery: ~(으)니까
- 가 보니까 정말 좋았어요. (When I went, it was really great.)
~(으)니까 in Questions
~(으)니까 can also be used when asking questions:
- 이미 했으니까 또 해야 돼요? (I already did it, so do I have to do it again?)
- 아니까 왜 또 물어봐요? (You know it, so why are you asking again?)
Common Mistakes
| Mistake | Correction | Why |
|---|---|---|
| 먹니까 (consonant stem) | 먹으니까 | Consonant stems need 으 |
| 가으니까 (vowel stem) | 가니까 | Vowel stems don't need 으 |
| Using ~아/어서 with commands | Use ~(으)니까 | 추워서 입으세요 (X) → 추우니까 입으세요 |
| 알으니까 | 아니까 | ㄹ drops before 니까 |
Summary
- ~(으)니까 means "because/since" with a strong, assertive nuance.
- Unlike ~아/어서, it works with commands and suggestions.
- Unlike ~아/어서, it allows past tense on the first clause.
- It has a unique discovery meaning: "when I did X, I found that Y."
- Formation: vowel stem + 니까, consonant stem + 으니까, ㄹ stem drops ㄹ + 니까.
- In casual speech, often shortened to ~(으)니 or ~(으)니깐.