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Connectives & Conjunctions

-아/어서 (aseo/eoseo) - Because/So

The connective ending -아/어서 (aseo/eoseo) expresses causality, showing that the first clause is the reason or cause for the second clause. It means "because," "so," or "since."

Basic Function

-아/어서 connects two clauses where the first clause provides the reason or cause for the second.

Translation: because, so, since, as

Usage: Expressing cause-effect relationships

Formation

Vowel Harmony Rule

After ㅏ or ㅗ → -아서:

  • 가다 → 가아서 → 가서 (because go)
  • 좋다 → 좋아서 (because good)
  • 작다 → 작아서 (because small)

After other vowels → -어서:

  • 먹다 → 먹어서 (because eat)
  • 크다 → 크어서 → 커서 (because big)
  • 없다 → 없어서 (because not exist)

With 하다 Verbs

-하 + 어서 → -해서:

  • 공부하다 → 공부해서 (because study)
  • 행복하다 → 행복해서 (because happy)
  • 깨끗하다 → 깨끗해서 (because clean)

Contractions

ㅏ/ㅓ + 아/어 → contraction:

  • 가 + 아서 → 가서
  • 서 + 어서 → 서서
  • 크 + 어서 → 커서

Basic Cause-Effect Pattern

Pattern: [Cause]아/어서 [Result]

Sequential reasoning:

  • 비가 와서 못 갔어요. (Because it rained, I couldn't go.)

  • 피곤해서 일찍 잤어요. (Because I was tired, I slept early.)

  • 배가 고파서 밥을 먹었어요. (Because I was hungry, I ate.)

  • 날씨가 좋아서 산책했어요. (Because the weather was good, I took a walk.)

Expressing Reasons

Why Questions

Q: 왜 안 갔어요? (Why didn't you go?) A: 바빠서** 못 갔어요.** (Because I was busy, I couldn't go.)

Q: 왜 샀어요? (Why did you buy it?) A: 좋아서** 샀어요.** (Because it was good, I bought it.)

Q: 왜 늦었어요? (Why were you late?) A: 차가 막혀서** 늦었어요.** (Because traffic was jammed, I was late.)

Sequential Actions

Natural Sequence

When the first action naturally leads to the second:

  • 집에 가서 쉬었어요. (I went home and rested.) - sequential

  • 샤워해서 기분이 좋아요. (I showered, so I feel good.) - result of action

  • 열심히 공부해서 합격했어요. (I studied hard, so I passed.) - cause-effect

With Action Verbs

Daily Activities

  • 일찍 일어나서 운동했어요. (I woke up early, so I exercised.)

  • 시간이 없어서 택시를 탔어요. (Because I didn't have time, I took a taxi.)

  • 친구를 만나서 영화를 봤어요. (I met a friend, so we watched a movie.)

Completed Actions Leading to Results

  • 아침을 먹어서 배가 안 고파요. (I ate breakfast, so I'm not hungry.)

  • 숙제를 다 해서 놀 수 있어요. (I finished homework, so I can play.)

With Descriptive Verbs (Adjectives)

States as Reasons

  • 추워서 코트를 입었어요. (Because it's cold, I wore a coat.)

  • 예뻐서 샀어요. (Because it's pretty, I bought it.)

  • 커서 마음에 들어요. (Because it's big, I like it.)

  • 비싸서 안 샀어요. (Because it's expensive, I didn't buy it.)

Emotional States

  • 기뻐서 울었어요. (Because I was happy, I cried.)

  • 슬퍼서 위로해 주었어요. (Because they were sad, I comforted them.)

  • 화가 나서 소리쳤어요. (Because I was angry, I shouted.)

Tense Restrictions

No Past Tense in First Clause

-아/어서 cannot take past tense marker -았/었:

❌ 비가 왔어서 못 갔어요. (incorrect) ✓ 비가 와서 못 갔어요. (correct)

❌ 피곤했어서 잤어요. (incorrect) ✓ 피곤해서 잤어요. (correct)

The past tense is shown only in the final clause.

Tense on Final Verb

  • 추워서 코트를 입었어요. (past)
  • 추워서 코트를 입어요. (present)
  • 추워서 코트를 입을 거예요. (future)

No Commands or Suggestions

Cannot Use with Imperative

❌ 추워서 코트를 입으세요. (incorrect) ✓ 추우니까 코트를 입으세요. (correct)

Use -(으)니까 instead for commands/suggestions.

Cannot Use with Propositive

❌ 배고파서 밥을 먹읍시다. (incorrect) ✓ 배고프니까 밥을 먹읍시다. (correct)

Irregular Verbs with -아/어서

ㅂ Irregular

ㅂ → 우 before vowel endings:

  • 춥다 → 추워서 (because cold)
  • 덥다 → 더워서 (because hot)
  • 아름답다 → 아름다워서 (because beautiful)
  • 쉽다 → 쉬워서 (because easy)

ㅎ Irregular

ㅎ drops, vowel changes:

  • 빨갛다 → 빨개서 (because red)
  • 하얗다 → 하애서 (because white)
  • 그렇다 → 그래서 (because so/therefore)
  • 어떻다 → 어때서 (because how)

으 Irregular

으 drops before vowel:

  • 크다 → 커서 (because big)
  • 예쁘다 → 예뻐서 (because pretty)
  • 바쁘다 → 바빠서 (because busy)
  • 아프다 → 아파서 (because sick/hurt)

ㄹ Irregular

ㄹ drops before certain endings:

  • 알다 → 알아서 (because know)
  • 살다 → 살아서 (because live)
  • 만들다 → 만들어서 (because make)

ㄷ Irregular

ㄷ → ㄹ before vowel:

  • 듣다 → 들어서 (because hear/listen)
  • 걷다 → 걸어서 (because walk)

ㅅ Irregular

ㅅ drops before vowel:

  • 낫다 → 나아서 (because better/healed)
  • 짓다 → 지어서 (because build)

Common Expression: 그래서

Standalone "Therefore/So"

그렇다 + -아서 = 그래서

Used as standalone conjunction:

  • 비가 와요. 그래서 못 가요. (It's raining. So I can't go.)

  • 바빠요. 그래서 못 도와줘요. (I'm busy. Therefore I can't help.)

  • 피곤해요. 그래서 쉬고 싶어요. (I'm tired. So I want to rest.)

Negative Reasons

Pattern: Negative 아/어서

  • 시간이 없어서 못 갔어요. (Because I didn't have time, I couldn't go.)

  • 돈이 없어서 못 샀어요. (Because I didn't have money, I couldn't buy it.)

  • 안 좋아서 안 샀어요. (Because it wasn't good, I didn't buy it.)

Expressing Gratitude/Apology

Pattern: [Action]아/어서 [감사/죄송]

Thanking:

  • 도와주셨어서 감사합니다. (Thank you for helping.) - lit: Because you helped, thank you

  • 와 주셔서 고맙습니다. (Thank you for coming.)

Apologizing:

  • 늦어서 죄송합니다. (I'm sorry for being late.) - lit: Because I'm late, sorry

  • 실수해서 미안해요. (I'm sorry for making a mistake.)

Multiple Reasons

Chaining -아/어서

Can chain multiple reasons:

  • 비가 와서 길이 막혀서 늦었어요. (Because it rained and the road was jammed, I was late.)

  • 날씨가 좋아서 시간도 있어서 나갔어요. (Because the weather was good and I had time, I went out.)

Explaining Situations

Pattern: [Situation]아/어서 [Explanation]

  • 오늘은 월요일이어서 바빠요. (Because today is Monday, I'm busy.)

  • 여기는 학교라서 조용해요. (Because this is a school, it's quiet.)

Note: Copula 이다 becomes -라서:

  • 학생이어서 → 학생이라서 (because is student)

Weather and Conditions

Weather as Reason

  • 비가 와서 우산을 가져왔어요. (Because it's raining, I brought an umbrella.)

  • 날씨가 좋아서 산책했어요. (Because the weather is nice, I took a walk.)

  • 더워서 에어컨을 켰어요. (Because it's hot, I turned on the AC.)

Health and Physical States

Physical Conditions as Reasons

  • 아파서 병원에 갔어요. (Because I was sick, I went to the hospital.)

  • 피곤해서 일찍 잤어요. (Because I was tired, I slept early.)

  • 배가 고파서 밥을 먹었어요. (Because I was hungry, I ate.)

Natural Consequences

Logical Results

  • 공부해서 시험을 잘 봤어요. (I studied, so I did well on the exam.)

  • 운동해서 건강해졌어요. (I exercised, so I became healthy.)

  • 열심히 일해서 성공했어요. (I worked hard, so I succeeded.)

Polite Explanations

Softening Refusals

  • 바빠서 못 가요. (I'm busy, so I can't go.) - polite refusal

  • 약속이 있어서 안 돼요. (I have an appointment, so I can't.) - polite refusal

  • 시간이 없어서 죄송해요. (I don't have time, so I'm sorry.)

With Different Subjects

Same Subject

  • 저는 피곤해서 쉬고 싶어요. (I'm tired, so I want to rest.)

Different Subjects (Less Common)

Usually requires clear context:

  • 날씨가 좋아서 기분이 좋아요. (The weather is good, so (I) feel good.)

  • 친구가 와서 기뻐요. (My friend came, so (I'm) happy.)

Contrast: -아/어서 vs -(으)니까

-아/어서

  • More neutral, objective reason

  • Cannot use with commands/suggestions

  • More about natural sequence

  • Softer, more conversational

  • 비가 와서 못 갔어요. (Because it rained, I couldn't go.)

-(으)니까

  • Can use with commands/suggestions

  • Emphasizes the reason more

  • More direct causality

  • Can sound stronger

  • 비가 오니까 우산을 가져가세요. (Since it's raining, take an umbrella.)

Common Mistakes

❌ Using Past Tense

Don't add -았/었 to -아/어서:

  • ❌ 먹었어서
  • ✓ 먹어서

❌ Using with Commands

Don't use with imperatives:

  • ❌ 추워서 입으세요
  • ✓ 추우니까 입으세요

Common Patterns

Daily Reasons

  • 늦어서 죄송해요. (Sorry for being late.)
  • 바빠서 못 가요. (Can't go because busy.)
  • 피곤해서 쉬고 싶어요. (Want to rest because tired.)

Natural Sequences

  • 집에 가서 쉬었어요. (Went home and rested.)
  • 일어나서 씻었어요. (Woke up and washed.)
  • 공부해서 합격했어요. (Studied and passed.)

Explanations

  • 비싸서 안 샀어요. (Didn't buy because expensive.)
  • 좋아서 샀어요. (Bought because good.)
  • 재미있어서 봤어요. (Watched because interesting.)