一旦

yīdàn

conjunction HSK 5 #1,028

Meanings

Literally "one dawn" - from the moment something happens.

HSK 4

一旦你开始学习，就会发现中文很有趣。

Yīdàn nǐ kāishǐ xuéxí, jiù huì fāxiàn Zhōngwén hěn yǒuqù.

Once you start learning, you'll find Chinese is very interesting.

HSK 5

一旦决定了，就不要后悔。

Yīdàn juédìng le, jiù búyào hòuhuǐ.

Once you've decided, don't regret it.

HSK 5

一旦发生火灾，请立即离开大楼。

Yīdàn fāshēng huǒzāi, qǐng lìjí líkāi dàlóu.

In case of fire, please leave the building immediately.

grammar

一旦…就… is a fixed pattern meaning "once… then…". The 就 part describes the consequence.

usage

一旦 often implies something irreversible or something with significant consequences. It's more dramatic than 如果 (if).

一 yī

旦 dàn