一...就 means "as soon as" or "once," showing that the second action happens immediately after the first.
Structure: 一 + Verb1，(Subject) + 就 + Verb2
Uses:
Sequence - 一看就懂 (understood at first glance)
Habitual - 一下雨就不想出門 (whenever it rains, don't want to go out)
Immediate reaction - 一聽就知道 (knew immediately upon hearing)
Without 就:
Sometimes 就 is omitted in casual speech:
• 一說他就生氣 → 一說他生氣
Similar patterns:
• 一...就... - As soon as (immediate)
• ...的時候 - When (general)
• ...以後 - After (less immediate)
See examples below for varied real-world usage.
一...就 = as soon as / whenever
- 一看就懂 (understand as soon as you see)
Immediate sequence or connection
- 一吃就飽 (full as soon as you eat)
Very common pattern
As soon as I get home, I do homework.
Once he heard it, he understood.
Whenever it rains, I do not want to go out.
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