-았/었더니
When I Did, After Doing
-았/었더니 connects a past action done by the speaker to a result or discovery. It means 'I did X, and then I found/realized Y' or 'Because I did X, Y happened'.
How It Works
-았/었더니 is a connective ending that attaches to a verb stem to link a past action performed by the speaker with a subsequent discovery or result. The first clause is always in the past tense, and the subject must be the speaker ('I' or 'we').
It has two primary functions:
1. Discovery or New Situation
The speaker performs an action and, as a result, discovers or encounters a new fact or situation. The subject of the first clause is the speaker, but the subject of the second clause can be different.
- 오랜만에 고향에 갔더니 많은 것이 변해 있었어요. (I went to my hometown for the first time in a while and found that many things had changed.)
- 창문을 열었더니 시원한 바람이 들어왔어요. (I opened the window, and a cool breeze came in.)
2. Cause and Effect
The speaker's past action is the direct cause of the result described in the second clause. In this case, the subject of both clauses is usually the speaker.
- 어제 늦게 잤더니 오늘 너무 피곤해요. (Because I went to bed late yesterday, I'm so tired today.)
- 매일 운동했더니 건강이 좋아졌어요. (I exercised every day, and as a result, my health improved.)
Conjugation:
It's formed by adding -았/었- to the verb stem, followed by -더니.
- Verb stem ending in ㅏ or ㅗ + -았더니 (e.g., 가다 → 갔더니, 보다 → 봤더니)
- Verb stem ending in other vowels + -었더니 (e.g., 먹다 → 먹었더니, 열다 → 열었더니)
- 하다 verbs → 했더니 (e.g., 공부하다 → 공부했더니)
Important Distinction: -았/었더니 vs. -더니
This is a critical point. -았/었더니 is used only for the speaker's actions (first-person). In contrast, -더니 is used when the speaker observes an action or state of someone or something else (third-person).
- I studied hard, and then I passed. → 제가 열심히 공부했더니 합격했어요. (Correct)
- My friend studied hard, and then he passed. → 친구가 열심히 공부하더니 합격했어요. (Correct, using -더니)
Examples (4)
- 어제 운동을 열심히 했더니 오늘 몸이 아파요.
I exercised hard yesterday, so my body aches today.
Word by Word: Yesterday exercise diligently did, so today body is sore.
This shows a direct cause-and-effect relationship. The speaker's action (exercising) caused the result (body aches).
- 오랜만에 친구에게 전화했더니 번호가 바뀌었어요.
I called my friend for the first time in a while and found out their number had changed.
Word by Word: After a long time to a friend called, so number had changed.
This shows a discovery. The speaker's action (calling) led to the discovery of a new fact (the number changed).
- 백화점에 갔더니 세일을 하고 있었어요.
I went to the department store and discovered they were having a sale.
Word by Word: To the department store went, so a sale was happening.
This shows a discovery. The speaker's action (going to the store) led to finding a new situation (a sale was happening).
- 커피를 너무 많이 마셨더니 잠이 안 와요.
I drank too much coffee, so now I can't sleep.
Word by Word: Coffee too much drank, so sleep doesn't come.
This shows a direct cause-and-effect relationship. The speaker's action (drinking coffee) caused the result (not being able to sleep).
Common Mistakes
Using -았/었더니 when the subject of the first action is not the speaker.
Different Meaning동생이 밥을 많이 먹었더니 배탈이 났어요.Better동생이 밥을 많이 먹더니 배탈이 났어요.-았/었더니 is used only when the speaker ('I') performs the first action. For observing an action done by someone else (like 'my brother') and its result, you must use -더니 instead.
Using -았/었더니 with adjectives in the first clause.
Not Quite어제 날씨가 좋았더니 기분도 좋아요.Better어제 날씨가 좋아서 기분이 좋았어요.The first clause must describe an action performed by the speaker, so it must be a verb. '날씨가 좋다' (the weather is good) is a description of a state, not an action. To express a simple reason like this, a different pattern such as -아/어서 is more natural.
Learn This First
To express results after action 'when I did/after doing', you need past tense and observation patterns.
Related Patterns
- -아/어서Because of, Therefore
Both can show cause and effect. -아/어서 is a general causal connector. -았/었더니 is more specific, emphasizing that the result was a direct consequence or discovery from the speaker's personal experience or action.
- -(으)니까So, Because
Both can express a reason. -니까 often provides a reason to justify a following command or suggestion. -았/었더니 focuses more on the temporal sequence and the discovery/result that followed the speaker's action, rather than just giving a reason.
- -다가 보니까After Doing for a While
Similar in that it involves a discovery after an action. -다가 보니까 implies that the discovery was made after continuing an action for some time, whereas -았/었더니 simply connects a completed past action to a subsequent discovery or result.