五、表示目的或用途

A knife is to cut with.
刀子是用来切东西的。

The telegram was to say that she'd be late. 电报是说她可能晚到。

六、表示推测或推断

He is not to be blamed. 不该责备他。

The book was not to be found.
那本书找不到了。

The account of the event is to be found in today's papers.
关于这件事的报道可在今天的报上找到。

七、表示命中注定

He was never to see his wife again. 他从那以后就再也见不到他的妻子了。

They were never to meet again. 他们注定以后永远不会再见面。

They said goodbye, little knowing that they were never to meet again.
他们相互道别，一点也没有想到他们再也不能相见了。

八、表示虚拟语气

即用于与事实相反的虚拟条件句，表示虚拟语气。此时be通常要用were这一形式，但在非正式文体中也可用was。如：

I'd be sorry if you were to think that I disliked you.
若是你认为我不喜欢你，那我就太伤心了。

If it were to rain, we would have to cancel the match tomorrow.
假如下雨, 我们只好取消明天的比赛。

注意其省略倒装形式：

If I were to tell you / Were I to tell you that I killed him, would you believe me? 假如我对你说是我杀死了他, 你相信吗?

If I were to do that / Were I to do that, what would you say? 如果我做了那件事，你会说什么呢?

说明：根据语意的需要，“be+不定式”结构中不定式可以用被动式。如：

The cover is not to be removed. 这块盖布请勿揭开。

This medicine is to be taken hourly. 这药每小时服一次。

The cost of carriage is to be paid by the receiver. 运费由收货人支付。

She will determine how it is to be done. 她会决定这件事的做法。

A little tiredness after taking these drugs is to be expected.
服下这些药后会有些疲倦。