英语条件状语从句的用法及有关说明

引导条件状语从句的从属连词有if, unless (=if…not如果不……，除非), as/so long as(只要), while(=as long as只要), supposing (that)/provided /providing (that)(假如), in case(假使), on condition that(在……的条件下)等。如：

You can learn anything so long as you set your mind to learn it. 用心学本领，总能学到手。

I will go there tomorrow unless it rains.(=…if it doesn’t rain)除非下雨，否则我明天要去那儿。

He will do the work providing you pay him. 如果你能付费，他可以做这工作。

In case l forget，please remind me about it. 如果我忘了，请提醒我。

We’ll let you use the room on condition that you keep it clean and tidy. 我们可以让你使用这个房间，条件是你把它保持整洁。

注：条件状语从句和时间状语从句一样，从句的谓语动词不能用一般将来时态、过去将来时态或将来完成时，而要用相应的一般现在时、一般过去时和现在完成时态来替代。又如：

Tell me in case you get into difficulty. 遇到困难请告诉我。

Supposing he does not come, shall we go without him? 如果他不来，是不是不带他去?

但若从句谓语用了will 或 would，那 will 或 would 则是表示“愿意”的情态动词。如：

If you will go with me, I’ll wait for you. 如果你愿意等我，我们就帮你做这事儿。