So/Because (-아/어서)
-아/어서
-아/어서 connects two clauses expressing reason ('because') or sequence ('and then').
Pattern
Verb/Adjective stem + 아서 (after ㅏ/ㅗ) / 어서 (after other vowels) / 해서 (하다 verbs)
Explanation
-아/어서 is a versatile connective ending with two main meanings. First, it expresses reason or cause: '배가 아파서 병원에 갔어요' (I went to the hospital because my stomach hurt). Second, it expresses sequential actions: '집에 가서 쉬세요' (Go home and rest).
The vowel harmony rules are the same as -아/어요: use -아서 after ㅏ/ㅗ vowels, -어서 after other vowels, and 해서 for 하다 verbs. Examples: 가다 → 가서, 먹다 → 먹어서, 공부하다 → 공부해서.
An important rule: when -아/어서 expresses reason, the tense is only marked on the final verb, not before -아/어서. You say '배가 아파서 병원에 갔어요' (not 아팠어서). This is different from -기 때문에, where tense can be marked. This rule is a common source of errors for learners.
Examples
배가 아파서 병원에 갔어요.
Bae-ga apaseo byeongwon-e gasseoyo.
I went to the hospital because my stomach hurt.
만나서 반갑습니다.
Mannaseo bangapseumnida.
Nice to meet you.
피곤해서 일찍 잤어요.
Pigonhaeseo iljjik jasseoyo.
I was tired so I slept early.
시장에 가서 과일을 샀어요.
Sijang-e gaseo gwail-eul sasseoyo.
I went to the market and bought fruit.
Common Mistakes
Wrong
배가 아팠어서 병원에 갔어요.
Correct
배가 아파서 병원에 갔어요.
When -아/어서 expresses reason, do not use past tense before it. Only the final verb takes tense.
Wrong
피곤하어서 잤어요.
Correct
피곤해서 잤어요.
하다 verbs contract: 하 + 여서 → 해서.
Related Grammar Points
Vocabulary in Examples
Practice vocabulary from these grammar patterns
Build your vocabulary with science-backed spaced repetition — 30 days free.
Start Practicing