in a very short time; in case; once

1. 你一旦了解她，就喜歡她了。
   You'll like her once you get to know her.
2. 他一旦下了決心就毫不動搖[無法使他改變（意見）]。
   Once he's made up his mind, he never budges/you can never budge him (from his opinion).
3. 一旦你掌握了煎蛋餅的技巧，做起來就很容易了。
   Making an omelette is easy once you've got the knack (of it).
4. 那盜賊下決心，一旦獲釋便重新做人。
   The thief was determined to turn over a new leaf once he was released from prison.
5. 政治家在選舉前空口許愿，一旦上臺就根本不是那麼回事了。
   Politicians promise the earth before an election, but things are different once they are in power.
6. 一旦下了決心，他就毫不動搖。
   Once he's made up his mind, he never budges.
7. 一旦開始，就必須繼續(xù)。
   Once you begin, you must continue.
8. 他一旦宣了誓，他就一直忠貞不渝。
   Once he took the vow his loyalty never wavered.

一的英語翻譯：

旦的英語翻譯：