lest
conjunction /lest/
/lest/
(formal or literary)- in order to prevent something from happening
免得；以免 - He gripped his brother's arm lest he be trampled by the mob.
他紧抓着他弟弟的胳膊，怕他让暴民踩着。 - Lest anyone should doubt my story, I have brought documents to attest to its truth.
以免有人怀疑我的故事，我带来了文件来证明它的真实性。
- He gripped his brother's arm lest he be trampled by the mob.
- used to introduce the reason for the particular emotion mentioned
（引出产生某种情感的原因）唯恐，担心 - She was afraid lest she had revealed too much.
她担心她泄露得太多了。
- She was afraid lest she had revealed too much.
词源Old English thȳ lǣs the ‘whereby less that’, later the læste.