一旦
HSK 4- Conditionals
Structure (结构 jiégòu)
Meaning (意思 yìsi)
一旦 is used to express a hypothetical future condition, carrying the meaning "once… then…".
Explanation (解释 jiěshì)
Use 一旦 (yīdàn) to introduce a hypothetical condition, emphasizing that once this condition occurs, the corresponding result will immediately follow. It is similar to "if" but carries a stronger nuance, referring to a decisive event or turning point. The following clause typically pairs with the adverb 就 or 便 to introduce the result.
Examples (例句 lìjù)(5)
- 一旦开始，就不要放弃。繁: 一旦開始，就不要放棄。Yīdàn kāishǐ, jiù bùyào fàngqì.
Once you start, don't give up.
- 你一旦撒谎，就没人信你了。繁: 你一旦撒謊，就沒人信你了。Nǐ yīdàn sāhuǎng, jiù méi rén xìn nǐ le.
Once you lie, nobody will believe you anymore.
- 这个问题一旦出现，就很难解决。繁: 這個問題一旦出現，就很難解決。Zhège wèntí yīdàn chūxiàn, jiù hěn nán jiějué.
Once this problem appears, it becomes very difficult to resolve.
- 他一旦决定了，就不会改变。繁: 他一旦決定了，就不會改變。Tā yīdàn juédìng le, jiù bù huì gǎibiàn.
Once he makes a decision, he will not change it.
- 机会一旦错过，就不会再来。繁: 機會一旦錯過，就不會再來。Jīhuì yīdàn cuòguò, jiù bù huì zài lái.
Once an opportunity is missed, it will not come again.
Common mistakes
- Wrong:我一旦昨天看见他了。Correct:我昨天一看见他，就跑了。
一旦 is not used for events that have already occurred in the past. To express 'as soon as... then...', use the structure '一...就...'.
- Wrong:一旦他有钱，他常常去旅游。Correct:只要他有钱，他就去旅游。
一旦 marks only an initial event. To express an ongoing or repeated condition ('whenever there is money'), 只要 (as long as) is more natural.