Word: 一旦 (yīdàn) 一旦 dictionary entry yīdàn in case (sth happens); if; once (sth happens, then...); when; in a short time; in one day Full dictionary entry for 一旦 Example sentences using 一旦 3 sentences, showing page 1 of 1. 一旦下雨，比赛就要取消。 Yídàn xiàyǔ, bǐsài jiùyào qǔxiāo. If it rains, the match will be cancelled. 一旦开始，就不要放弃。 Yídàn kāishǐ, jiù búyào fàngqì. Once you start, don't give up. 思维一旦僵化，就很难创新。 Sīwéi yídàn jiānghuà, jiù hěn nán chuàngxīn. Once your thinking becomes rigid, it's hard to be innovative.