Korean -(으)니까: "Because" Before Requests, and "When I..."
Learn -(으)니까, the Korean "because" you can use before requests and suggestions. See how to build it, how it differs from -아서/어서, and its "when I did X" use.
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The short answer
Add -(으)니까 to a verb to say “because” or “since”. Unlike -아서/어서, it can come before a request or a suggestion: 추우니까 코트 입으세요 (It’s cold, so wear a coat). It also has a second meaning: “when I did X, I found...”
If you have read about -아서/어서, you already know one way to say “because”. But that ending has a rule: no commands or suggestions after it. So how do you say “It’s raining, so take an umbrella”? That is the job of -(으)니까. Tap the chips below to see each part.
1. How to make it
Take the dictionary form, drop 다, and look at the last sound of the stem.
- Ends in a vowel: add 니까 (가니까, 바쁘니까)
- Ends in a consonant: add 으니까 (먹으니까, 많으니까)
- Ends in ㄹ: drop the ㄹ, add 니까 (사니까, 머니까)
| Dictionary form | Meaning | Because (now) | Because (past) |
|---|---|---|---|
| 가다 | to go | 가니까 | 갔으니까 |
| 바쁘다 | to be busy | 바쁘니까 | 바빴으니까 |
| 먹다 | to eat | 먹으니까 | 먹었으니까 |
| 없다 | to not have | 없으니까 | 없었으니까 |
| 살다 | to live | 사니까 | 살았으니까 |
| 춥다 | to be cold | 추우니까 | 추웠으니까 |
| 듣다 | to listen | 들으니까 | 들었으니까 |
| 하다 | to do | 하니까 | 했으니까 |
| 학생이다 | to be a student | 학생이니까 | 학생이었으니까 |
춥다 and 듣다 are irregular, just like in the polite form (추워요, 들어요). With a noun, use 이니까 after a consonant and 니까 after a vowel: 시험이니까, 친구니까.
2. A reason, then a request or suggestion
This is the main reason to learn -(으)니까. When the second half says “please do”, “let’s” or “shall we”, this is the “because” to use.
춥다 is a ㅂ irregular: the ㅂ turns into 우, so you get 추우니까.
3. The past tense is allowed
With -아서/어서, the past tense goes only on the last verb. With -(으)니까, you can put the past tense right on the reason: 았/었 + 으니까.
4. “When I did X, I found...”
-(으)니까 has a second meaning that surprises many learners. It can mean “when I did this, I found out that...” The first half is what you did. The second half is what you saw or discovered, and it is in the past tense.
The first verb stays in the present form (가니까). 갔으니까 would mean 'because I went'.
열다 drops its ㄹ before 니까: 여니까.
You will often hear this with 보다 (to try): 먹어 보니까 means “when I tried eating it, I found...”
5. -(으)니까 vs -아서/어서
Both mean “because”, and in a plain statement you can often use either one. Here is where they part ways.
| Situation | -아서/어서 | -(으)니까 |
|---|---|---|
| Plain reason | 바빠서 못 가요 | 바쁘니까 못 가요 |
| Before a request or suggestion | No | 바쁘니까 나중에 만나요 |
| Past tense on the reason | No | 비가 왔으니까 |
| Sorry and thank you | 늦어서 죄송해요 | No |
| “When I did X, I found...” | No | 가니까 없었어요 |
There is also a difference in feeling. -아서/어서 just reports a cause. -(으)니까 points at the listener a little, like “since, you see...” That is why it sounds wrong in an apology: 늦었으니까 죄송해요 sounds like an excuse, not a real “sorry”.
6. 니까요 and 그러니까 in conversation
Add 요 and you can use -(으)니까 on its own, as a short answer to “why?”
Said with a sharp tone, 니까요 can sound like 'I already told you!' Keep your voice soft.
그러니까 starts a sentence with “so” or “that’s why”. In everyday talk it also means “I mean...” or “Exactly!” You will hear it constantly in dramas.
Keep going
Song lyrics love 니까, often in lines like “since you’re here” or “because I love you”. Open a song in Hanbok Lyrics and tap a line to see each ending explained. Compare with -아서/어서 (because, and then), learn the -아/어 보다 (try doing) pattern, or see how -(으)면 (if) uses the same 으 rule.
Check yourself
Quick check · 1 of 4먹다 (to eat) + -(으)니까 = ?
먹 ends in a consonant.
Questions learners ask
What does 니까 mean in Korean?
-(으)니까 means "because" or "since". It joins a reason to what comes next: 비가 오니까 우산을 가져가세요 (It is raining, so take an umbrella). It can also mean "when I did X, I found...": 집에 가니까 아무도 없었어요 (When I got home, nobody was there).
What is the difference between 아서/어서 and 니까?
Both give a reason. Only -(으)니까 can be followed by a request, command or suggestion, and only -(으)니까 can take the past tense (갔으니까). For apologies and thanks, use -아서/어서: 늦어서 죄송해요.
When do I use 으니까 and when 니까?
After a vowel, add 니까 (가니까, 바쁘니까). After a consonant, add 으니까 (먹으니까, 많으니까). Stems ending in ㄹ drop the ㄹ and add 니까: 살다 becomes 사니까, 열다 becomes 여니까.
What does 그러니까 mean?
그러니까 means "so" or "that is why" at the start of a sentence. In conversation it also means "I mean" or "exactly", when you agree with someone or explain yourself again.