Grammar
-던/-았던
Meaning
Advanced-deon/-atdeon
A retrospective modifier that recalls a past state, action, or habit from the speaker's memory, often implying it is no longer the case now. -던 describes something ongoing, repeated, or left unfinished in the past ('used to be/do'), while -았/었/였던 describes something that was already completed at that time ('had been/had done'), viewed now in hindsight.
Form
Attach 던 directly to a verb, adjective, or 이다 stem with no vowel change, to recall an ongoing/repeated/habitual past state: 살다 → 살던 (used to live), 예쁘다 → 예쁘던. For a completed past action recalled now, insert the past marker first: 았/었/였 + 던 → 가다 → 갔던 (had gone), 하다 → 했던. Both forms directly precede a noun, functioning as a modifier ('the N that used to/had ~').
Examples
누리호 2단부에 사용될 예정이었던 인증시험용 엔진이었다.
It was a certification-test engine that had been scheduled for use in Nuri's second stage.
제가 어렸을 때 살던 동네예요.
This is the neighborhood I used to live in as a child.
작년에 갔던 식당에 다시 갔어요.
I went again to the restaurant I had visited last year.
Common mistakes & nuance
-던 does not necessarily mean the action is finished — it can describe something interrupted, repeated, or still going on at that past moment. -았/었/였던 marks that the action was already completed, so the two are not interchangeable: 먹던 빵 ('the bread [I] was eating') vs 먹었던 빵 ('the bread [I] had eaten').
Similar grammar
- -았/었/였고
-았/었/였고 uses the same past-tense markers (았/었/였) but attaches 고 to connect two full clauses in a sentence ('did A, and did B'). -던/-았던 attaches to a stem to modify a following noun, recalling a past state rather than connecting clauses.