“A, so it’s B.”
“Since it’s C, I think it’s D.”

It is important to explain something to others and to share your opinion.

That is why we want to be able to speak smoothly, but let’s practice so that we can do it in Korean as well.

Grammar that talks about causes, reasons, etc.

Speak on the basis of evidence.

-아서/어서 is the grammar used when talking about causes and reasons.

Causes and reasons.

①너무 바빠요.
I’m so busy.

그래서 공부를 못 해요.
That’s why I can’t study.


③너무 바빠서 공부를 못 해요.
I can’t study because I’m very busy.

Think of it this way, two sentences combined into one.

Similar to the usage of “-아요/어요”.

“-아서/어서” also change the combination to match the stem of the verb or adjective.

Vst + 아서/어서/여서

사다 + -아서 = 사서
좋다 + -아서 = 좋아서
아프다 + -아서 = 아파서

먹다 + -어서 = 먹어서
춥다 + -어서 = 추워서
예쁘다 + -어서 = 예뻐서

공부하다 + 여서 = 공부해서
필요하다 + 여서 = 필요해서

※Vst = stem of verbs or adjectives.

The usage is similar to “-아요/어요”.

The stem vowel has ‘아,오’.

방이 좁아서 좀 불편해요.
The room is small and a little inconvenient.
옷을 많이 사서 월급날까지 돈이 없어요.
I bought a lot of clothes and I have no money until payday.

No ‘아,오’ in the vowels.

많이 먹어서 배가 불러요.
We eat a lot and we are full.
술을 많이 마셔서 속이 안 좋아요.
I’ve had too much to drink and I’m suffering from a hangover.

Usage of the word 하다

언니는 착해서 남자들한테 인기 많아요.
My sister is kind and popular with men.
많이 취해서 혼자서 못 걸어요.
I’m so drunk I can’t walk alone.

If you don’t understand -아요/어요, you won’t be able to keep up with the changes in conjugation, so if you don’t have a basic understanding of the -요 body, this is a good time to review.

Variable case conjugation is also a “-아요/어요” rule.

The usage of irregular conjugation is almost the same as -아요/어요.

10시간 동안 계속 걸어서 다리가 아픕니다.
I’ve been walking for 10 hours straight and my feet hurt.
안에서 문을 잠가서 밖에서 못 열어요.
I locked the door from inside, so I can’t open it from outside.

If your memory is fuzzy on this one, too, review it carefully.

When you want to use “-아서/어서” with a noun?

Use “-이어서” for nouns.

-아서/어서 also use -이다 when used with nouns.

저 손목시계는 한정판이어서 엄청 비싸요.
That watch is incredibly expensive because it’s a limited edition.
다음 주는 여자친구 생일이어서 선물을 살 거예요.
Next week is her birthday and I’m going to buy her a gift.

If you change -이다 according to the -아서/어서 rule, you get -이어서.

You can also use “-라서” for nouns.

Often, -라서 is used instead of -이어서.

내가 다이어트중이라서 케이크는 참아요.
I’m on a diet, so I’m cutting back on the cake.
그는 아직은 미성년자라서 술을 마시지 못합니다.
He is still underage and cannot drink alcohol.

In the case of nouns with patches, the 이 is inserted and becomes -이라서.

Notes on using “-아서/어서”.

You can leave it as it is, even if it’s in the past.

Be careful when using -아서/어서 with the past tense.

-아서/어서 & the past tense.

어제는 너무 바빴어요.
Yesterday was very busy.


어제는 너무 바빴어서 (×)

When talking about the past, it is not “-았/었어서”.

You use -아서/어서 for the present tense.

어제는 내가 정신이 없어서 깜빡했어요.
I was incredibly busy yesterday and just forgot about it.
슈퍼가 문을 닫아서 두부를 못 샀습니다.
Supermarkets were closed and I couldn’t buy tofu.

If you use the past tense at the end of the sentence, there is no problem.

Cannot be used for imperative or solicitation statements.

Also, know that -아서/어서 cannot be used in imperative or solicitous sentences.

바닥이 미끄러워서 조심해요. (×)
김치가 너무 매워서 먹지 마십시오. (×)

Be careful not to use 아서/어서 in imperative sentences.

Let’s use -아서/어서 to give a reason in Korean at once.