왜냐하면 (That's because)

왜냐하면 is used to introduce an explanation or reason. It means "that's because," "the reason is," or "it's because."

Structure

Statement. 왜냐하면 Explanation + -기 때문이다/-(으)니까/-(으)ㄹ까요

Breakdown:

• 왜: Why
• 냐하면: If you ask
• Combined: "If you ask why..." → "That's because..."

Usage: Introduces the reason after stating a fact or claim

Basic Pattern

Introducing Explanation

Pattern 1: Statement. 왜냐하면 Reason + ending.

Examples:

• 못 갔어요. 왜냐하면 아팠기 때문이에요
  (I couldn't go. That's because I was sick.)

• 좋아해요. 왜냐하면 재미있으니까요
  (I like it. That's because it's fun.)

Common Sentence Endings with 왜냐하면

With -기 때문이다

Most common formal pattern:

• 왜냐하면 ... -기 때문이다/이에요/입니다

Examples:

• 안 갔어요. 왜냐하면 바빴기 때문이에요
  (I didn't go. That's because I was busy.)

• 좋아요. 왜냐하면 예쁘기 때문이에요
  (It's good. That's because it's pretty.)

With -(으)니까

Natural spoken pattern:

• 왜냐하면 ... -(으)니까요

Examples:

• 못 먹어요. 왜냐하면 배부르니까요
  (I can't eat. That's because I'm full.)

• 안 샀어요. 왜냐하면 비싸니까요
  (I didn't buy it. That's because it was expensive.)

With -거든요

Casual explanation:

• 왜냐하면 ... -거든요

Examples:

• 못 가요. 왜냐하면 바쁘거든요
  (I can't go. That's because I'm busy.)

Formality Level

More Formal

Compared to simple 그래서:

• 왜냐하면 → More structured, explanatory
• 그래서 → More casual, conversational

Used in:

• Written explanations
• Formal presentations
• Academic contexts
• Structured arguments
• When emphasizing reasoning

Common Usage Patterns

Answering "Why" Questions

Q: 왜 안 왔어요? (Why didn't you come?) A: 왜냐하면 아팠기 때문이에요 (That's because I was sick)

Q: 왜 좋아해요? (Why do you like it?) A: 왜냐하면 재미있으니까요 (That's because it's fun)

Making Arguments

Stating claim then explaining:

• 이 방법이 좋습니다. 왜냐하면 효과적이기 때문입니다
  (This method is good. That's because it's effective.)

• 운동이 중요합니다. 왜냐하면 건강에 좋으니까요
  (Exercise is important. That's because it's good for health.)

Shortened Form: 왜냐면

Casual Version

왜냐하면 → 왜냐면 (contracted)

More casual, spoken:

• 못 가요. 왜냐면 바빠요
  (I can't go. That's because I'm busy.)

• 좋아요. 왜냐면 맛있어요
  (It's good. That's because it's delicious.)

Usage: Casual conversation, less formal

In Conversation

Natural Dialogue Flow

A: 이 식당 좋아해요?
(Do you like this restaurant?)

B: 네, 좋아해요. 왜냐하면 음식이 맛있으니까요.
(Yes, I like it. That's because the food is delicious.)

---

A: 왜 늦었어요?
(Why are you late?)

B: 죄송해요. 왜냐하면 교통이 막혔기 때문이에요.
(Sorry. That's because traffic was bad.)

Position in Discourse

Beginning of Explanation Sentence

Always starts the explanation:

• Statement. 왜냐하면 explanation.

Not used mid-sentence:

• ✗ 아파 왜냐하면 못 갔어요
• ✓ 못 갔어요. 왜냐하면 아팠기 때문이에요

Contrast with Similar Expressions

왜냐하면 vs 그래서

왜냐하면: "That's because" (explaining reason)

• 좋아해요. 왜냐하면 재미있으니까요
  (I like it. That's because it's fun.)
• → Emphasizes explanation

그래서: "So" (showing result)

• 재미있어요. 그래서 좋아해요
  (It's fun. So I like it.)
• → Shows result/consequence

Key difference: Direction of reasoning

• 왜냐하면: Result → Reason
• 그래서: Reason → Result

왜냐하면 vs -기 때문에

왜냐하면: Standalone introducer + sentence

• 좋아요. 왜냐하면 맛있기 때문이에요
  (It's good. That's because it's delicious.)

-기 때문에: Grammatical ending within sentence

• 맛있기 때문에 좋아요
  (Because it's delicious, it's good.)

Example Dialogues

Dialogue 1: Preference

A: 커피를 안 마셔요?
(You don't drink coffee?)

B: 네, 안 마셔요. 왜냐하면 카페인에 민감하기 때문이에요.
(No, I don't. That's because I'm sensitive to caffeine.)

Dialogue 2: Choice

A: 왜 이 학교를 선택했어요?
(Why did you choose this school?)

B: 왜냐하면 프로그램이 좋으니까요.
(That's because the program is good.)

Dialogue 3: Opinion

A: 이 영화 좋아하세요?
(Do you like this movie?)

B: 아니요, 안 좋아해요. 왜냐하면 너무 길기 때문이에요.
(No, I don't. That's because it's too long.)

Dialogue 4: Absence

A: 어제 회의에 왜 안 왔어요?
(Why didn't you come to yesterday's meeting?)

B: 죄송합니다. 왜냐하면 급한 일이 있었기 때문입니다.
(I'm sorry. That's because I had an urgent matter.)

In Writing

Formal Essays

Making arguments:

• 이 정책은 효과적입니다. 왜냐하면 많은 연구가 이를 뒷받침하기 때문입니다
  (This policy is effective. That's because much research supports this.)

Reports

Explaining findings:

• 결과가 좋습니다. 왜냐하면 방법이 적절했기 때문입니다
  (The results are good. That's because the method was appropriate.)

Common Mistakes

❌ Incorrect: 왜냐하면 아파요

Missing proper ending

✅ Correct: 왜냐하면 아프기 때문이에요

Need -기 때문이다 or similar ending

---

❌ Incorrect: 아파요 왜냐하면 못 갔어요

Wrong order

✅ Correct: 못 갔어요. 왜냐하면 아팠기 때문이에요

Statement first, then 왜냐하면 explanation

---

❌ Incorrect: 왜냐하면 그래서

Mixing different connectives

✅ Correct: 왜냐하면 ... -기 때문이에요

Complete the pattern properly

Usage Notes

More Common in Formal Contexts

Everyday speech:

• Often just use -아/어서 or -(으)니까
• 왜냐하면 can sound formal/stilted

Better for:

• Presentations
• Essays
• Formal arguments
• Structured explanations

Casual Alternatives

Instead of: 못 가요. 왜냐하면 바빠요. More natural: 바빠서 못 가요. (I'm busy, so I can't go.)

Summary Table

Expression	Direction	Formality	Usage
왜냐하면	Result → Reason	Formal	Introducing explanation
그래서	Reason → Result	Casual	Showing consequence
-기 때문에	Within sentence	Formal	Written reason
-아/어서	Within sentence	Casual	Spoken reason

Pattern Comparison

Pattern	Example	Natural in
왜냐하면 + -기 때문이다	왜냐하면 바빴기 때문이에요	Formal speech/writing
왜냐하면 + -(으)니까	왜냐하면 바쁘니까요	Spoken explanation
왜냐면 + ending	왜냐면 바빠요	Casual speech

Key Takeaways

✅ Introduces explanation: "That's because..."
✅ After statement: Explains previous claim
✅ Needs proper ending: -기 때문이다, -(으)니까, -거든요
✅ More formal: Than simple -아/어서
✅ Can shorten: 왜냐하면 → 왜냐면 (casual)
✅ Direction: Result → Reason (opposite of 그래서)

왜냐하면 is useful for structured, formal explanations where you want to clearly introduce your reasoning. While less common in casual daily conversation (where -아/어서 or -(으)니까 are more natural), it's valuable for presentations, essays, and situations requiring clear, formal explanations.