Giving a Reason

There are several ways to give a reason in Korean. Let’s cover the three most common, (으)니까, 서 and 때문 form.

Saying because using (으)니까

Verb Stem + (으)니까

1. Get the verb stem.
2. Attach 으니까 if it ends in a Consonant, or attach 니까 if it ends in a vowel.
   • However, for verb stems that end with the consonant ㄹ, remove it and attach 니까.
     For example: 살다 → 사니까
   • However, for verb stems that end with the consonant ㅂ, remove it and attach 우, then 니까.
     For example: 맵다 → 매우니까
3. Finish the rest of the sentence, or attach 요 if it’s used at the end of a sentence.

The reason will always come before the because form (this applies to any because form).

The (으)니까 form is not a formal sounding grammar form, although it’s also not impolite. The more formal version would be xxx which is covered further below.

Example sentences using the (으)니까 form

음식이 뜨거우니까 조심하세요.

Be careful because the food is hot.

사과가 차가우니까 더 맛있어요.

The apple is more delicious because it is cold.

저는 매일 일을 하고 있으니까 항상 바빠요.

I am always busy because I am working every day.

제가 한국 사람 아니니까요.

It's because I'm not Korean.

Limitations of the (으)니까 form

Exceptions for when using (으)니까 is not possible:

• (으)니까 can not be used to say someone feels some sort of emotion ‘because’ of something. So you cannot use this form to say you are happy, sad, thankful or sorry. For this you have to use the 서 form.

Saying because using 서

Verb Stem Conjugated + 서

1. Get the verb stem.
2. Conjugate as usual with 아 or 어, without attaching 요 at the end.
3. Attach 서.

Building the form examples:

• 하다: 해서
• 먹다: 먹어서
• 살다: 살아서
• 맵다: 매워서

This 서 also translate to because, but it shows more emphasis of a cause and effect. Using this 서 form emphasizes that that something was caused by something else.

Example sentences using the 서 form

머리가 아파서 병원에 갔어요.

I went to the hospital because my head hurt.

어제 무서워서 잠을 잘 수 없었어요

Yesterday I couldn't sleep because I was scared.

조금 피곤해서요.

Because I'm a little tired.

일찍 와 줘서 고마워요.

Thank you for coming early.

Limitations of the 서 form

Exceptions for when using 서 is not possible:

• The 서 form can not be used when giving a reason for a command. Only (으)니까 can be used for that, e.g. 오늘 날씨 좋으니까 밖에서 만나세요. needs the (으)니까 form.
• The 서 form can not be used for making a suggestion. Only (으)니까 can be used for that, e.g. 오늘 날씨 좋으니까 밖에서 만날까요? needs the (으)니까 form.

Saying because using 때문

The 때문 form is more common in writing than in speaking. It also means because but sounds more straightforward and more like a written expression. Therefore it’s used in formal situation or in writing.

There are several ways to use the 때문 form.

때문 simply at the end of a sentence

The most basic form for it:

Noun + 때문

This form makes the noun the reason, so because of NOUN.

Example sentences:

그 문제 때문이에요.

It's because of that problem.

제가 매운 음식을 먹을 수 없기 때문이에요.

It's because I can't eat spicy food.

때문 in the middle of a sentence

To use the 때문 form in the middle of a sentence attach the particle 에:

Noun + 때문에

Example sentences:

제가 매운 음식을 먹을 수 없기 때문에 김치도 먹을 수 없어요.

I also can't eat Kimchi because I can't eat spicy food.

맛있는 음식을 많이 먹었기 때문에 배가 불러요.

I am full because I ate a lot of delicious food.

이 김치를 좋아하기 때문에 세 통을 샀어요.

I bought three containers because I like this Kimchi.

저는 한국어를 배웠기 때문에 한국인 친구들이 많이 있어요.

I have a lot of Korean friends because I learned Korean.

Limitations of the 때문 form

The 때문 form has the same limit as the 서 form, it cannot be used when giving someone a command or when making a suggestion.

When using the 때문 form after a person it means you’re blaming the person for something. For example:

이게 다 아빠 때문이에요.

This is all because of dad.

To instead thank someone use the 덕분 form after a person. 덕분 means thanks to. For example:

이게 다 아빠 덕분이에요.

This is all thanks to dad.

Using the past tense

The (으)니까 and 때문 form, like many other forms, can be attached to a verb stem in the past tense.

To get the past tense verb stem, conjugate the verb into the past tense as usual, then remove 어요. The remaining stem ends in the consonant ㅆ, so attach 으니까.

• 하다 → 했어요 → 했 → 했으니까
• 먹다 → 먹었어요 → 먹었 → 먹었으니까

The past-tense marker should not normally be used with the 서 form. Instead, tense is marked on the final verb, while the time of the 서 clause is understood from context.

The important difference is:

머리가 아파서 병원에 갔어요.

I went to the hospital because my head hurt.

• The final 갔어요 establishes the past setting.

머리가 아팠으니까 병원에 갔어요.

I went to the hospital because my head hurt.

• The 아팠으니까 explicitly marks the reason itself as past.

머리가 아팠기 때문에 병원에 갔어요.

I went to the hospital because my head hurt.

• Like (으)니까, the 때문 form can be attached to the past tense stems.

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Sources & References

• Billy Go’s Beginner Korean Course | #70: Giving a Reason Part 1
• Billy Go’s Beginner Korean Course | #71: Giving a Reason Part 2