Overview
~아/어서 is one of the most frequently used connectors in Korean. It has two main functions:
- Cause/Reason -- "because" or "so"
- Sequential connection -- "and then" (especially with movement verbs)
This connector follows the same vowel harmony rules as the present tense ~아/어요.
How to Form ~아/어서
| Stem vowel | Ending | Example |
|---|---|---|
| ㅏ or ㅗ (bright) | ~아서 | 가다 → 가서, 좋다 → 좋아서 |
| Other vowels (dark) | ~어서 | 먹다 → 먹어서, 없다 → 없어서 |
| 하다 verbs | ~해서 | 하다 → 해서, 공부하다 → 공부해서 |
The same vowel contraction rules as ~아/어요 apply:
| Dictionary | Stem | + 아/어서 | Result |
|---|---|---|---|
| 가다 | 가 | 가 + 아서 | 가서 |
| 오다 | 오 | 오 + 아서 | 와서 |
| 먹다 | 먹 | 먹 + 어서 | 먹어서 |
| 마시다 | 마시 | 마시 + 어서 | 마셔서 |
| 배우다 | 배우 | 배우 + 어서 | 배워서 |
| 하다 | 하 | 하 + 여서 | 해서 |
| 바쁘다 | 바쁘 | 바쁘 + 어서 | 바빠서 |
| 피곤하다 | 피곤하 | 피곤하 + 여서 | 피곤해서 |
Part 1: Cause and Reason ("Because / So")
~아/어서 connects a reason in the first clause to a result in the second clause.
Basic examples
- 배가 고파서 밥을 먹었어요. (Because I was hungry, I ate.)
- 날씨가 좋아서 산책했어요. (Because the weather was nice, I took a walk.)
- 피곤해서 일찍 잤어요. (Because I was tired, I slept early.)
- 시간이 없어서 못 갔어요. (Because I had no time, I couldn't go.)
- 비가 와서 우산을 샀어요. (Because it rained, I bought an umbrella.)
Fixed expressions
Some ~아/어서 expressions are used as set phrases:
| Expression | Meaning | Usage |
|---|---|---|
| 만나서 반갑습니다 | Nice to meet you | First meetings |
| 만나서 반가워요 | Nice to meet you (casual) | First meetings |
| 늦어서 죄송합니다 | Sorry for being late | Apologizing |
| 늦어서 미안해요 | Sorry for being late (casual) | Apologizing |
| 감사해서... | Because I'm grateful... | Thanking |
Part 2: Sequential Connection ("And Then")
With movement verbs (가다, 오다, 들어가다, 나가다, etc.), ~아/어서 means "go/come and then (do something there)."
- 도서관에 가서 공부했어요. (I went to the library and studied.)
- 한국에 와서 한국어를 배웠어요. (I came to Korea and learned Korean.)
- 카페에 들어가서 커피를 마셨어요. (I went into the cafe and drank coffee.)
- 집에 와서 쉬었어요. (I came home and rested.)
This is different from the pure "and" connector ~고. With ~아/어서, the second action happens at the destination or as a result of the movement.
| ~고 | ~아/어서 | Difference |
|---|---|---|
| 서울에 가고 부산에 갔어요 | 서울에 가서 쇼핑했어요 | ~고 lists separate events; ~아/어서 shows action at destination |
Critical Rule: No Commands or Suggestions
~아/어서 cannot be used with commands (imperative) or suggestions (propositive) in the second clause.
| Incorrect | Correct | Connector to use |
|---|---|---|
| 비가 와서 우산 가져오세요 (X) | 비가 오니까 우산 가져오세요 | ~(으)니까 |
| 더우니까 에어컨 켜세요 (O) | 더워서 에어컨 켜세요 (X) | ~(으)니까 |
| 배고파서 밥 먹자 (X) | 배고프니까 밥 먹자 | ~(으)니까 |
| 시간 없어서 빨리 가세요 (X) | 시간 없으니까 빨리 가세요 | ~(으)니까 |
This is one of the most important differences between ~아/어서 and ~(으)니까.
When to use which
| Second clause type | Use ~아/어서? | Use ~(으)니까? |
|---|---|---|
| Statement | O | O |
| Question | O | O |
| Command (-세요) | X | O |
| Suggestion (-자, -(으)ㅂ시다) | X | O |
Critical Rule: No Past Tense on First Clause
With ~아/어서, the first clause does not take past tense. The tense of the entire sentence is determined by the final verb.
| Incorrect | Correct | Why |
|---|---|---|
| 배가 고팠어서 먹었어요 (X) | 배가 고파서 먹었어요 | No past tense before ~아/어서 |
| 비가 왔어서 안 갔어요 (X) | 비가 와서 안 갔어요 | No past tense before ~아/어서 |
| 피곤했어서 쉬었어요 (X) | 피곤해서 쉬었어요 | No past tense before ~아/어서 |
Compare with ~(으)니까, which does allow past tense on the first clause: - 비가 왔으니까 안 갔어요. (O -- past tense okay with ~(으)니까)
~아/어서 vs. ~(으)니까
| Feature | ~아/어서 | ~(으)니까 |
|---|---|---|
| Commands/Suggestions | X (cannot use) | O (can use) |
| Past tense on 1st clause | X (cannot use) | O (can use) |
| Tone | Softer, more natural | Stronger, more assertive |
| "I discovered that..." | X | O (discovery meaning) |
| Fixed expressions | 만나서 반갑습니다 | 반가우니까... (unusual) |
~아/어서 vs. ~고
Both can express sequential actions, but with different nuances:
| ~아/어서 | ~고 | Difference |
|---|---|---|
| 가서 먹었어요 | 가고 먹었어요 | ~아/어서: went and ate there; ~고: went, and also ate |
| 앉아서 기다렸어요 | 앉고 기다렸어요 | ~아/어서: sat down and waited (in seated state); ~고: sat, then waited |
~아/어서 often implies the first action sets up or enables the second, while ~고 simply lists.
Subject Restriction
When ~아/어서 expresses cause/reason, the subject of both clauses is often the same. When subjects differ, ~(으)니까 is sometimes preferred:
- (Same subject) 피곤해서 쉬었어요. (I was tired so I rested.)
- (Different subjects) 비가 와서 경기가 취소됐어요. (It rained so the game was canceled.) -- This is acceptable.
Different subjects are grammatically fine with ~아/어서, especially when the relationship is clearly causal.
Common Mistakes
| Mistake | Correction | Why |
|---|---|---|
| 추워서 문 닫으세요 | 추우니까 문 닫으세요 | Can't use ~아/어서 with commands |
| 비가 왔어서 | 비가 와서 | No past tense before ~아/어서 |
| 좋아어서 | 좋아서 | ㅏ+ㅏ merges, don't add extra 어 |
| 해어서 | 해서 | 하+여 = 해 + 서 |
Summary
- ~아/어서 expresses cause/reason ("because") and sequential action ("and then").
- Follows the same vowel harmony rules as ~아/어요.
- Cannot be used with commands (~세요) or suggestions (~자) in the second clause -- use ~(으)니까 instead.
- No past tense allowed on the first clause -- tense goes on the final verb only.
- With movement verbs, it means "go/come somewhere and then do something there."
- Common fixed expressions: 만나서 반갑습니다, 늦어서 죄송합니다.