6. 用于 if only 含有“但原(愿)”，“要是…就好了”。其用法wish基本相同。
If only he know(had known) how we missed him!
If only he were alive.
If only I hadn’t made such a mistake!
来源：考试大
7. 用于otherwise 或or 引导的并列句中。
I don’t know where he is, otherwise(or) I would telephone him.
来源：考试大
8. 用在lest, in order that, in case引导的目的状语从句中。
He told his wife as little as possible, lest she (should) spread the news all over town.
来源：考试大
9. 用在as if, as though引导的方式状语从句中。
She spoke to me as if I were deaf.(表同时或之后发生)
She behaved as if nothing had happened.(表从句动作在主句动作之前发生)
