一旦…就…
Once…, (then)…
HSK 5HSK 3.0 · 5
一旦 + condition/event，(S) + 就 + result
一旦 introduces something that may happen (often sudden or significant), with the second clause as the inevitable consequence, 'once…': 一旦失去健康，有钱也没用. 一旦 may come before or after the subject, and the second clause usually has 就. Unlike 一…就… (one action immediately after another, descriptive), 一旦 is hypothetical and typically warns of serious or irreversible consequences.
HSK 5 reading (argumentative/advice passages) and gap fills.
Examples
一旦失去健康，有钱也没用。
Once you lose your health, money is useless.
这种习惯一旦养成，就很难改。
Once this habit forms, it's hard to break.
一旦发现问题，就要马上报告。
Report any problem as soon as you find it.
他一旦决定了，谁也改变不了。
Once he's decided, nobody can change his mind.
Exercises
1. 出现火灾，就要马上打119。
2.机会一旦错过， 很难再有了。
3.Choose the correct sentence:
4.“信任一旦失去，就很难找回来。”意思是：