Core Pattern Rule: Connecting Observation to Outcome
The pattern -더니 is used to connect two clauses, where the first clause is an action or state that the speaker directly observed or experienced, and the second clause is the resulting change or subsequent event.
Meaning & Usage
Meaning: It translates to "(I saw/experienced) X, and then Y happened" or "because of X, Y happened." It emphasizes that the speaker is reporting on something they personally witnessed.
When to use: Use it to show a cause-and-effect relationship, a sequence of events, or a contrast between a past observation and the present situation.
Formation
Attach -더니 directly to the stem of a verb or adjective, regardless of whether it ends in a vowel or a consonant.
먹다 (to eat) → 먹더니
공부하다 (to study) → 공부하더니
오다 (to come) → 오더니
To indicate that the first action is complete, you can use the past tense form -았/었더니.
먹었다 (ate) → 먹었더니
열심히 공부하더니 합격했어. / 비가 오더니 갑자기 추워졌어. / 아기가 울더니 잠들었어요.
Who is the Subject? (1st vs. 3rd Person)
The rules for using -더니 change depending on the subject of the sentence. This is a key point for using it correctly.
Third-Person Subject (he, she, it, they)
When the subject is someone or something else, the subject of the first clause and the second clause must be the same. The speaker is simply an observer.
(그가) 열심히 공부하더니 (그가) 합격했어요. → (He) studied hard, and then (he) passed.
First-Person Subject (I, we)
When the subject of the first clause is the speaker (나 or 우리), the pattern is almost always used in its past tense form, -았/었더니.
The second clause describes a new fact, discovery, or result that the speaker realized after performing the action. The subject of the second clause can be different from the first.
(내가) 약을 먹었더니 (내 몸이) 좋아졌어요. → (I) took the medicine, and (as a result, I found that my body) got better. The subject stays the same ('I').