赖世雄教你学英语语法
虚拟语气
5-7：lest...should...
lest为连接副词，引导副词从句。在该从句中，助动词一律用should。而should往往予以省略，故该从句中的一般动词必定是原形动词。
例：i got up early lest i (should) miss the train.
（我早起以免错过火车。）
i came on time lest he (should) be angry.
（我准时到，免得他生气。）
注意
lest...should...
=for fear that...may（表现在或将来的状况）
=for fear that...might（表过去的状况）
=for fear of + 动名词
例：you must study hard lest you should fail the exam.
= you must study hard for fear that you may fail the exam.
= you must study hard for fear of failing the exam.
（你必须用功念书，以免考试失败。）
he did it carefully lest he should make a mistake again.
= he did it carefully for fear that he might make a mistake again.
= he did it carefully for fear of making a mistake again.
（他很谨慎地做这件事，惟恐再次犯错。）