五、表示目的或用途

A knife is to cut with.
刀子是用來切東西的。

The telegram was to say that she'd be late. 電報是說她可能晚到。

六、表示推測或推斷

He is not to be blamed. 不該責備他。

The book was not to be found.
那本書找不到了。

The account of the event is to be found in today's papers.
關于這件事的報道可在今天的報上找到。

七、表示命中注定

He was never to see his wife again. 他從那以后就再也見不到他的妻子了。

They were never to meet again. 他們注定以后永遠不會再見面。

They said goodbye, little knowing that they were never to meet again.
他們相互道別，一點也沒有想到他們再也不能相見了。

八、表示虛擬語氣

即用于與事實相反的虛擬條件句，表示虛擬語氣。此時be通常要用were這一形式，但在非正式文體中也可用was。如：

I'd be sorry if you were to think that I disliked you.
若是你認為我不喜歡你，那我就太傷心了。

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

注意其省略倒裝形式：

If I were to tell you / Were I to tell you that I killed him, would you believe me? 假如我對你說是我殺死了他, 你相信嗎?

If I were to do that / Were I to do that, what would you say? 如果我做了那件事，你會說什么呢?

說明：根據語意的需要，“be+不定式”結構中不定式可以用被動式。如：

The cover is not to be removed. 這塊蓋布請勿揭開。

This medicine is to be taken hourly. 這藥每小時服一次。

The cost of carriage is to be paid by the receiver. 運費由收貨人支付。

She will determine how it is to be done. 她會決定這件事的做法。

A little tiredness after taking these drugs is to be expected.
服下這些藥后會有些疲倦。