Korean Clause Connectors 아/어서 VS. (으)니까 — What’s the difference?
What’s the difference between the Korean clause connectors 아/어서 and (으)니까?
아/어서 (Verb ending with vowel ㅏ and ㅗ → 아서 ; Otherwise → 어서)
The 2 main usages of 아/어서:
1. Shows reasons and causes — has the meaning of “because”
저는 배고파서 밥을 먹고 싶어요. = I want to eat because I’m hungry. *The first half is the reason for the second half
2. Shows sequence — has the meaning of “then”
저는 학교에 가서 친구를 만났어요. = I went to school, then I saw some friends.
(으)니까
Verb ending with a consonant (받침) → 으니까 ; Otherwise → 니까
1. Shows reasons and causes — has the meaning of “because”
날씨가 추우니까 따뜻하게 입으세요. = Since it is cold, please wear warmly. *The first half is the reason for the second half
2. Shows discovery — realizes the second action after finishing the first action
아침에 일어나니까 9시였어요. = It was 9 when I woke up in the morning.
Similarities:
아/어서 and (으)니까 are similar because they both express cause and effect, but they also have 2 differences.
Differences:
1. 아/어서 cannot be used in imperatives and propositive sentences, but (으)니까 can be used in all 4 types of sentences *Click here to review them!
늦어서 빨리 가자.(X)
늦었으니까 빨리 가자.(O)
= It’s late, so let’s go!
→ 빨리가자 is a propositive ending, so we have to use (으)니까 instead of 아/어서
오늘 추워서 따뜻하게 입으세요. (X)
오늘 추우니까 따뜻하게 입으세요. (O)
= Since today is cold, please wear warmly.
→ 으세요 is a polite way of asking or suggesting, so we have to use (으)니까 instead of 아/어서
2. 아/어서 cannot be conjugated into other tenses, just show the tense change at the end of the sentence. Instead, (으)니까 needs to be conjugated accordingly.
The following sentences both have the meaning of “I was tired, so I slept early”, but the way the past tense is incorporated is different.
피곤해서 일찍 잤어요.
피곤했으니까 일찍 잤어요.
Both sentences are correct, but have you noticed the difference? 아/어서 will not change because of the change in tense (피곤해서), while (으)니까 needs to be conjugated appropriately (피곤했으니까). It’s important to note that both sentences have shown the past tense at the end of the sentences (일찍 잤어요). *Click here to review the past tense of Korean!
