Conjunctions - Because [때문에]

Conjunctions - Because [때문에; 왜냐하면, 때문이다]

때문에 is more frequently used in written Korean and ~서 is favoured in spoken Korean because of its brevity.

Rules  

Take 다 off a plain form and past tenses of verbs and adjectives and then attach 기 때문에. (But NOT a present tense of verbs ie. 한다 → 한기 때문에 is wrong! 하다 → 하기 때문에 is right!)  

• 하다 → 하기 때문에 = Because I do
  
• 가다 → 가기 때문에 = Because I go
• 사다 → 사기 때문에 = Because I buy
• 보다 → 보기 때문에 = Because I see
• 먹기 → 먹기 때문에 = Because I eat
• 좋아하다 → 좋아하기 때문에 = Because I like
  
• 했다 → 했기 때문에 = Because I did
• 갔다 → 갔기 때문에 = Because I went
• 먹었다 → 먹었기 때문에 = Because I ate
• 크다 → 크기 때문에 = Because it's big
• 작다 → 작기 때문에 = Because it's small
• 덥다 → 덥기 때문에 = Because it's hot
• 춥다 → 춥기 때문에 = Because it's cold
  
• 많다 → 많기 때문에 = Because there is a lot 
• 길다 → 길기 때문에 = Because it's long
• 맛있다 → 맛있기 때문에 = Because it's delicious 
• 높았다 → 높았기 때문에 = Because it was high 
  
• 예뻤다 → 예뻤기 때문에 = Because it was pretty
  
• 빨랐다 → 빨랐기 때문에 = Because it was fast
• 강했다 → 강했기 때문에 = Because it was strong

Example sentences 
- Compare and contrast 때문에 and ~서.

• 중국음식을 좋아하기 때문에 중국음식을 먹었다. = Because I like Chinese food, I ate Chinese food. (Written Korean)
• 중국음식 좋아하기 때문에 중국음식 먹었어요. = Because I like Chinese food, I ate Chinese food. (Spoken Korean)
• 중국음식 좋아해서 중국음식 먹었어요 = Because I like Chinese food, I ate Chinese food. (Spoken Korean) Conjunctions - Because, So
• 아침 일찍 학교를 가기 때문에 일찍 일어났다. = Because I go to school early in the morning, I got up early.
• 아침 일찍 학교 가서 일찍 일어났어요 = Because I go to school early in the morning, I got up early.
• 겨울에는 춥기 때문에 사람들은 따뜻한 옷을 입는다. = Because the winter is cold, people wear warm clothes.
• 겨울엔 추워서 사람들은 따뜻한 옷을 입어요 = Because the winter is cold, people wear warm clothes.
• 인터넷에는 잘못된 정보가 많기 때문에 무엇을 읽는지 조심해야 한다. = Because on the internet, there is a lot of false information, we should be careful about what we read.
• 인터넷엔 잘못된 정보가 많아서 뭘 읽는지 조심해야 되요. = Because on the internet, there is a lot of false information, we should be careful about what we read

Note: The object particle, 를/을, is omitted and some words are abbreviated in the spoken form. For example,

• 에는 →엔
• 무엇을 → 무얼 → 뭘
  

Although it is less commonly used, a sentence containing two clauses can be divided into two sentences using 왜냐하면 and 때문이다. 왜냐하면 is attached to the front of a second clause and 때문이다 replaces 때문에.

• 중국음식을 먹었다. 왜냐하면 중국음식을 좋아하기 때문이다. = I ate Chinese food because I like Chinese food.
• 중국음식 먹었어요. (왜냐면) 중국음식 좋아해서요. = I ate Chinese food because I like Chinese food.
• 일찍 일어났다. 왜냐하면 아침 일찍 학교를 가기 때문이다. = I got up early because I go to school early in the morning.
• 일찍 일어났어요. (왜냐면) 아침 일찍 학교 가서요. = I got up early because I go to school early in the morning.

Note:

왜냐하면 is abbreviated to 왜냐면 or it is altogether omitted in spoken Korean.

때문에 is mainly used in literature and the news reporters use it often. However, people still use 때문에 occasionally in conversations instead of ~서, especially when one wants to explain and reason.