[Grammar] -아/어/여서 ‘Because’, reasons

-아/어/여서 Because

We already know 그래서. 그래서 means ‘therefore’ or ‘so’ which expresses reason and result. For example,
오늘 비가 많이 왔어요. 그래서 날씨가 추워요. It rained a lot today, so it is cold.
오늘 아침을 안 먹었어요. 그래서 지금 정말 배가 고파요. I didn’t eat breakfast, so I am so hungry now.
돈이 없어요. 그래서 여행 못 가요. I don’t have money, so I can’t go travel.
시간이 없어요. 그래서 파티에 갈 수 없어요. I don’t have time, so I can’t go to the party.

As you can see, those are two separate sentences. In real conversations, we combine those two sentences in on sentence and we use -아/어/해서 to combine a reason and a result.

-아/어/여서 has two meanings. The first one is “because” and the second one is “and then” which is sequence of two actions. If you learn more about the second meaning, please click here. This post is about ‘reason and result’.


1. When a verb/adjective stem ends with ‘아/오’ vowel  + 아서

i.e) – 비가 오(다) => 오(ㅗ vowel) +아서

– 잠을 못 자(다) => 자(ㅏ vowel) + 아서

2. When a verb/adjective stem ends with other vowels besides ‘아/오’ + 어서

– 밥을 안 먹(다) => 먹(ㅓ vowel) + 어서

– 술을 마시(다) => 마시(ㅣ vowel) + 어서

– 아직 안 배우(다) => 배우(ㅜ vowel) + 어서

3. When a verb or an adjective stem ends with ‘하’  + 여서 => 하여 =>

– 공부를 안 하(다) + 여서 => 공부를 안 해서

– 피곤하(다) + 여서 => 피곤해서

비가 와서 날씨가 시원해요. Because it rains, it is cool.
어제 잠을 못 자서 피곤해요. Because I didn’t sleep well yesterday, I am tired.
밥을 안 먹어서 배가 고파요. Because I haven’t had a meal, I am hungry.
어제 술을 많이 마셔서 머리가 아파요. Because I drank a lot yesterday, I have a headache.
아직 안 배워서 몰라요. Because I haven’t learned yet, I don’t know.
공부를 안 해서 시험을 못 봤어요. Because I didn’t study, I didn’t do well on my exam.
어제 피곤해서 잠을 많이 잤어요. Because I was tired, I slept a lot.

You can listen to the pronunciation on my Quizlet.com (Click here).

As you can see on those sentences, you can’t add the tense in front of -아/어/여서 even though the event happened in the past.  If you want to express the tense, you can add the tense verb ending at the end of the sentence.

One more thing, you can’t use a suggestion sentence or an imperative sentence with -아/어/여서. For example,

Because the weather is nice, let’s go for a walk.  날씨가 좋아서 같이 산책해요.(X)
Because it rains, don’t go outside. 비가 와서 밖에 나가지 마세요.(X)
Because the tickets are sold out, can we see it tomorrow?  오늘 표가 없어서 내일 볼까요?(X)

If you want to use a suggestion or an imperative sentence, you should use -(으)니까.

Because the weather is nice, let’s go for a walk.  날씨가 좋으니까 같이 산책해요. (O)
Because it rains, don’t go outside. 비가 오니까 밖에 나가지 마세요.(O)
Because the tickets are sold out, can we see it tomorrow?   오늘 표가 없으니까 내일 볼까요?(O)

You can click here to learn more about -(으)니까.

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