-자 (시간)
the moment that — written style
A literary “as soon as.” Identical in shape to the propositive -자 meaning “let’s,” but a completely different ending.
Build it
Pick a verb
When to use it
Attach -자 to any action verb stem — no vowel rule, ㄹ stays, no tense in front. The two clauses may have different subjects.
It marks immediate succession, often with a sense that the second event followed naturally from the first: 수업이 끝나자 학생들이 교실을 나갔다.
Two things separate it from -자마자. It belongs to writing — novels, news, reports — and sounds stiff in conversation. And it takes no commands or suggestions after it, where -자마자 accepts them freely.
Telling it apart from the propositive is a matter of position: the time ending sits mid-sentence with a clause after it, while “let’s” ends the sentence.
How to attach it
| Situation | Form | Example |
|---|---|---|
| Any action verb | -자 | 끝나다 → 끝나자 |
| ㄹ stems keep the ㄹ | -자 | 열다 → 열자 |
| Different subjects | allowed | 수업이 끝나자 학생들이 나갔다 |
| No commands after | statements only | 도착하자 전화하세요 is wrong |
| Never takes tense | plain stem only | 끝났자 is wrong |
| Spoken version | -자마자 | 끝나자마자 |
In use
수업이 끝나자 학생들이 교실을 나갔다.
The moment class ended, the students left the room.
문을 열자 찬바람이 들어왔다.
As soon as the door opened, cold air rushed in.
그 소식을 듣자 모두 자리에서 일어섰다.
On hearing the news, everyone rose from their seats.
해가 지자 거리가 조용해졌다.
Once the sun set, the streets grew quiet.
공연이 시작하자 관객들이 조용해졌다.
As the performance began, the audience fell silent.
비가 그치자 사람들이 밖으로 나왔다.
When the rain stopped, people came outside.
Compared with
-자마자
Same meaning, different register and different flexibility. -자마자 works in speech and takes commands; -자 belongs to written narrative and does not.
도착하자마자 전화하세요. (call on arrival) / 도착하자 전화가 왔다. (as he arrived, a call came)
-자 (let’s)
Identical form, unrelated meaning. Position tells them apart: the propositive closes a sentence, the time ending links two clauses.
같이 가자. (let’s go) / 그가 가자 방이 조용해졌다. (once he left, the room fell quiet)
-(으)니까
-(으)니까 can also mark discovery on doing something, but adds a causal or explanatory flavour. -자 reports pure sequence.
문을 여니까 찬바람이 들어왔어요. (I opened it and found) / 문을 열자 찬바람이 들어왔다. (the instant it opened)
Watch out
집에 도착하자 전화하세요.
집에 도착하자마자 전화하세요.
-자 cannot be followed by a command. For an instruction, -자마자 or -는 대로 is needed.
수업이 끝났자 학생들이 나갔다.
수업이 끝나자 학생들이 나갔다.
-자 never carries tense. The past is expressed once, on the final verb.
야, 비가 그치자 나갔어.
야, 비가 그치자마자 나갔어.
-자 is a written form. In casual speech it sounds oddly formal; use -자마자.
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