一旦

once

in case (something happens)

in one day

一旦[yīdàn]

-（一天之间）inasingleday;inaveryshorttime:
bedestroyedinoneday;毁于一旦
collapseovernight溃于一旦
-（不确定的时间）once;incase;nowthat:

你一旦了解她，就喜欢她了。
You'll like her once you get to know her.

他一旦下了决心就毫不动摇[无法使他改变（意见）]。
Once he's made up his mind, he never budges/you can never budge him (from his opinion).

一旦你掌握了煎蛋饼的技巧，做起来就很容易了。
Making an omelette is easy once you've got the knack (of it).

那盗贼下决心，一旦获释便重新做人。
The thief was determined to turn over a new leaf once he was released from prison.

政治家在选举前空口许愿，一旦上台就根本不是那麽回事了。
Politicians promise the earth before an election, but things are different once they are in power.

一旦下了决心，他就毫不动摇。
Once he's made up his mind, he never budges.

一旦开始，就必须继续。
Once you begin, you must continue.

他一旦宣了誓，他就一直忠贞不渝。
Once he took the vow his loyalty never wavered.

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