Reasons and explanations

아/어서 is one of the most common Korean connectors for giving a reason. It connects a cause with a result and often means “because” or “so”.

The structure is Reason + 아/어서 + Result. For example, 비가 와서 집에 있어요 means “Because it is raining, I stay home.” Korean often places the reason first and the result second.

Use 아서 after stems with ㅏ or ㅗ, and 어서 after many other vowels. With 하다 verbs, the form becomes 해서. For example, 바쁘다 becomes 바빠서, 먹다 becomes 먹어서, and 공부하다 becomes 공부해서.

This connector is very useful in daily life because it lets you explain naturally: why you are late, why you cannot go, why you are tired, or why something happened.

For 하다 verbs, 아/어서 becomes 해서. This is extremely common because many Korean verbs are made from Noun + 하다: 공부하다, 일하다, 운동하다, 청소하다, 전화하다, and many more.

For example, 공부하다 becomes 공부해서, meaning “because I studied”. 일하다 becomes 일해서, meaning “because I worked”. 운동하다 becomes 운동해서, meaning “because I exercised”.

This form is useful when explaining your condition or result. 일해서 피곤해요 means “I am tired because I worked.” 운동해서 배고파요 means “I am hungry because I exercised.”

Once you know 해서, you can explain many things quickly because 하다 verbs are everywhere in Korean.

때문에 means “because of”. It is often used after nouns to give a reason. Compared with 아/어서, it can sound a little more direct or cause-focused.

The basic pattern is Noun + 때문에 + Result. For example, 비 때문에 늦었어요 means “I was late because of the rain.” 일 때문에 바빠요 means “I am busy because of work.”

You can also use it after a clause with 기 때문에, but at the elementary level, it is enough to start with noun reasons: 날씨 때문에, 일 때문에, 시험 때문에, 아이 때문에.

This pattern is very useful when explaining an external reason: weather, work, traffic, exam, illness, schedule, or family situation.

그래서 means “so” or “therefore”. It is used at the beginning of a second sentence to show the result of the previous sentence.

Unlike 아/어서, which connects two parts inside one sentence, 그래서 often connects two separate sentences. For example: 비가 와요. 그래서 집에 있어요. means “It is raining. So I am staying home.”

This is very useful when speaking in simple, clear Korean. You can state the reason first, then use 그래서 to introduce the result.

For learners, 그래서 is a powerful tool because it lets you explain ideas without building long complex sentences immediately.

왜냐하면 means “because”. It is often used when you give an explanation after making a statement. It works like a signal that a reason is coming.

A common structure is Statement. 왜냐하면 Reason. For example, 오늘 못 가요. 왜냐하면 일이 있어요. means “I cannot go today. Because I have work.”

In natural Korean, people often use shorter reason forms like 아/어서 or 때문에, but 왜냐하면 is very useful for learners because it clearly marks explanation.

You can think of 왜냐하면 as a bridge for longer speaking. First say your main point. Then use 왜냐하면 to explain why.