-자마자
-jamaja
Not a sliver of gap: -자마자
The picture The door clicks shut and the next thing springs out on that same click. No gap between the two. -자마자 pins the second event to the exact point the first one ends, while -(으)ㄴ 후에 accepts anywhere after it — 졸업하자마자 취직했어요 leaves no gap, but 졸업한 후에 취직했어요 is still true if it took months.
Where the picture shows up in -자마자
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on the click of the door
집에 오자마자 씻었어요.
ji-be o-ja-ma-ja ssi-seo-sseo-yo
The moment I got home, I took a shower.
The front door clicks shut, the bag hits the floor, and you are already walking into the bathroom.
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pouring in with no gap
문이 열리자마자 사람들이 몰려들었어요.
mu-ni yeol-li-ja-ma-ja sa-ram-deu-ri mol-lyeo-deu-reo-sseo-yo
The instant the doors opened, people flooded in.
The instant the doors part, a wall of shoulders pushes through all at once.
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out the door on answering
전화를 받자마자 뛰어나갔어요.
jeon-hwa-reul bat-ja-ma-ja ttwi-eo-na-ga-sseo-yo
I took the call and ran straight out.
The receiver is not even off your ear before the chair slides back and your body turns for the door.
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where one chapter ends
졸업하자마자 취직했어요.
jo-reo-pa-ja-ma-ja chwi-ji-kae-sseo-yo
I got a job right after graduating.
The same hand that takes off the graduation gown hangs an employee badge around the neck.
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lights out on lying down
눕자마자 잠들었어요.
nup-ja-ma-ja jam-deu-reo-sseo-yo
I fell asleep the moment I lay down.
The eyes close at the exact moment the head touches the pillow.
Never put a past-tense marker before -자마자. 오자마자 is right; 왔자마자 is wrong.
All of it in one picture
-자마자 pins the second event onto the sound of the first one ending. The front door clicks and the bathroom door opens; the doors part and people pour in; the call is answered and the body is already out of the chair. Let the hand that takes off a graduation gown hang up a badge and one chapter locks into the next; let the eyes close on the sound of head meeting pillow and there is no gap at all. So between two events joined by -자마자 there is no room to slip in even a 'in a moment'.