✍️ Intermediate Day 18: Expressing Cause – ~(으)니까 vs ~아/어서

📘 Intermediate Day 18: Expressing Cause – ~(으)니까 vs ~아/어서

Welcome to Day 18 of the Intermediate Korean series! 😊 Today’s lesson is all about expressing reason or cause using two of the most frequently used grammar structures in Korean:

  • ~(으)니까 – because / so / since
  • ~아/어서 – because / so / and then

They can seem similar, but they have different nuances and specific situations where they are more appropriate. Let’s learn how to use both clearly and naturally!

📘 1. ~아/어서 – Expressing Natural Cause or Sequence

This form is used when the first clause is a natural cause or reason for the second clause. It can also show a sequence of actions.

🔧 How to form:

  • Verb stem + 아서 (for stems with ㅏ or ㅗ)
  • Verb stem + 어서 (for all other vowels)
  • 하다 → 해서

📌 Examples:

  • 배가 고파서 밥을 먹었어요.
    bae-ga go-pa-seo bap-eul meo-geo-sseo-yo
    👉 I was hungry, so I ate.
  • 날씨가 좋아서 산책했어요.
    nal-ssi-ga jo-a-seo san-chaek-hae-sseo-yo
    👉 The weather was nice, so I took a walk.
  • 공부해서 피곤해요.
    gong-bu-hae-seo pi-gon-hae-yo
    👉 I studied, so I’m tired.

❌ Important: ~아/어서 cannot be used in imperative or propositional sentences (like “Please do…” or “Let’s go…”).


📘 2. ~(으)니까 – Expressing Subjective or Logical Reason

~(으)니까 is used when the speaker gives a subjective reason or when they are making a request, suggestion, or command based on a cause.

🔧 How to form:

  • Ends in vowel → + 니까 (가다 → 가니까)
  • Ends in consonant → + 으니까 (먹다 → 먹으니까)

📌 Examples:

  • 늦었으니까 빨리 가요!
    neu-jeot-eu-ni-kka ppal-li ga-yo
    👉 Because it’s late, let’s go quickly!
  • 비가 오니까 우산을 가져가요.
    bi-ga o-ni-kka u-san-eul ga-jyeo-ga-yo
    👉 Since it’s raining, take an umbrella.
  • 배가 고프니까 뭐 먹자.
    bae-ga go-peu-ni-kka mwo meok-ja
    👉 I’m hungry, so let’s eat something.

📌 Comparison Table – ~아/어서 vs ~(으)니까

Structure Usage Can use with Commands? Example
~아/어서 Natural reason / Cause-and-effect ❌ No 아파서 병원에 갔어요
~(으)니까 Logical or subjective reason ✅ Yes 배고프니까 밥 먹자

💬 Real-Life Dialogue

👦 준호: 왜 이렇게 일찍 왔어요?
👧 수지: 길이 막힐까 봐서 일찍 출발했어요.
👦 준호: 잘했네요. 비 오니까 우산 가져왔어요?


📘 Practice Sentences

  • 더워서 아이스크림을 먹었어요.
  • 날씨가 추우니까 옷을 따뜻하게 입으세요.
  • 집에 일찍 가니까 저녁을 준비할게요.
  • 너무 피곤해서 일찍 잤어요.

🧪 Mini Quiz – Cause and Effect

  1. Translate: “Because I was sick, I didn’t go to school.”
    Click to Show Answer

    아파서 학교에 안 갔어요.

  2. Translate: “Let’s go together because it’s dangerous.”
    Click to Show Answer

    위험하니까 같이 가요.

  3. Which is correct for command?
    a) 늦었어서 빨리 가세요
    b) 늦었으니까 빨리 가세요
    Click to Show Answer

    ✅ b) 늦었으니까 빨리 가세요


✅ Conclusion

👏 Great work! Now you can clearly express causes and reasons in Korean with:

  • ✔️ ~아/어서 – natural cause, sequence (no commands)
  • ✔️ ~(으)니까 – subjective or logical cause (with commands allowed)


📘 Coming Up Next

Tomorrow: Intermediate Day 19: Expressing Effort – ~도록 / ~(으)려고 노력하다 Let’s learn how to say “I try to…” or “in order to…”

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