引导条件状语从句的连词

if:

I must leave if that's the case. 如果情况如此我就得走了。

What would Diana think of him if he failed? 如果他失败，戴安娜会对他怎么想？

If she said so, she's a liar. 如果她这样讲了，她就是撒谎。

If true, this will cause us a lot of trouble. 如果是真的，这会给我们造成很多麻烦。

If necessary, ring me at home. 必要的话往我家里打电话。

He will come if asked. 如果邀请的话他是会来的。

If convenient, I'll be with you next Tuesday. 如方便的话，我将于下星期二和你见面。

unless:

I won't write unless he writes first. 我不写信，除非他先给我写。

Unless I'm mistaken, I've seen that man before. 除非我记错了，那人我以前见过。

I'll go there tomorrow unless it rains. 除非下雨，否则我明天去那里。

He'd never do this unless compelled. 除非被迫，否则他决不会这样做。

Unless redeemed, it'll be for sale. 除非有人赎回，否则它将出售。

supposing:

Supposing that he asks you, will you go? 假定他请你去，你会去吗？

Supposing his plan goes wrong, what will we do then? 如果他的计划出了问题，我们怎么办？

Supposing you're wrong, what will you do then? 假如你错了你怎么办？

suppose:

Suppose she finds out, what shall we do then? 假如她发现了，我们怎么办？

Suppose you lost your job tomorrow, what would you do? 假定你明天失业，你怎么办？

provided:

I will agree to go provided(providing)(that)my expenses are paid. 如果有人给我掏路费我将同意去。

She agreed to go and work there provided that her family could go with her. 如果她家人能随她同行，她同意去那里工作。

providing:

I'll dry the dishes, providing that you do the washing-up. 如果你刷盘子，我就把它们擦干。

You will always have a home as long as I have anything. 只要我有家产，你就永远会有一个家。

I don't mind your knowing anything as long as it goes no further. 你知道什么我都不介意，只要你不告诉别人。

In case he arrives before I get back, please ask him to wait. 如果我还没回来他就到了，请让他等一等。

They'll stand by you even if you don't succeed. 即使你不成功他们也会支持你。

Were I Tom I would refuse. 如果我是汤姆，我会拒绝。

Should you require anything, just let me know. 如果你需要什么，告诉我就行。

Had I thought of it, I'd have talked to mother. 如果我想过这事，我早就和妈讲了。

此外，as long as, so long as, in case, even if都起连词作用。