Observed Change (-더니)
-더니
Connects a past observation to a resulting change: 'I noticed... and then...'
Pattern
Verb stem + -더니 (3rd person observation) / -았/었더니 (1st person past action + result)
Explanation
-더니 connects something the speaker observed in the past to a subsequent change or result. It has two main uses: sequential observation and contrasting observation.
Sequential: 열심히 공부하더니 시험에 합격했어요 (I saw them studying hard, and they passed the exam). Contrasting: 아까는 웃더니 지금은 울어요 (Earlier they were laughing, but now they're crying).
Important restriction: when used for third person, the first clause describes what the speaker observed about someone else. For first person, the first clause uses past tense -았/었더니 to describe a past action and its result: 많이 먹었더니 배가 아파요 (I ate a lot and now my stomach hurts).
Examples
비가 오더니 이제 그쳤어요.
Biga odeoni ije geuchyeosseoyo.
It was raining, and now it has stopped.
매일 운동하더니 살이 빠졌어요.
Maeil undonghadeoni sari ppajyeosseoyo.
They were exercising every day, and they lost weight.
많이 걸었더니 다리가 아파요.
Mani georeotdeoni dariga apayo.
I walked a lot, and now my legs hurt.
아까는 맑더니 지금은 흐려요.
Akkaneun makdeoni jigeumeun heuryeoyo.
It was clear earlier, but now it's cloudy.
Common Mistakes
Wrong
제가 공부하더니 합격했어요.
Correct
열심히 공부했더니 합격했어요.
For 1st person, use past tense -았/었더니 (reporting your own action and result).
Wrong
내일 비가 오더니 추울 거예요.
Correct
비가 오더니 추워졌어요.
-더니 reports past observations, not future predictions.
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