3.由其他连词引导的条件状语从句

条件状语从句通常由if引导，已如上述。除if外，还有许多其他从属连词可以引导条件状语从句，如unless，provided(that)，providing(that)，supposing(that)，in case，assuming that，given that，as/so long as，on condition that等，有时引导时间状语从句的从属连词when也可引导条件状语从句。由这些连词引导的条件状语从句也有真实条件与非真实条件之分。(详见虚拟语气)

(1)用unless引导。

①由unless引导的条件状语从句既可以是真实条件，也可以是非真实条件。作为真实条件状语从句，unless通常相当于if．．not。

The United Nations AIDS agency warns that the number of infected people in China could reach 10 million by 2020 unless more is done to prevent the spread of the disease．(人教大纲版高三第76页)(unless more is done=if no more is done)

联合国艾滋病机构警告说，如果不采取更多的措施来预防这种疾病的蔓延，那么到2020年，中国被艾滋病感染的人数可能达到一千万。

We should never try to revive a person unless we knowhow to do it．(人教大纲版高二上第60页)(unless we know=if we don't know)

除非懂得如何使人复苏，否则不要动手。

We can't write to Mr．White unless he sends us his address(unless he sends us his address=if he doesn't send us his address)．

如果怀特先生不把他的地址寄给我们，我们就不可能给他写信。

②如果unless从句本身是个否定句，那么unless就不可以为if．．not所取代。

You will get a good grade in the course unless you don't do your homework．

这门课程是可以取得好成绩的，除非你不做作业。

在这里，当然不可以．．if you don't not do your homework，两个not不可以重叠使用。

当unless从句表示非真实条件时，unless有时也不可以为if．．not所取代。

They couldn't afford to live in such a beautiful apartment unless they were rich．

他们住不起那样漂亮的公寓，除非很富有。

这是一个表示与现在事实相反的非真实条件句，如果把unless从句改为if they were not rich，就与原意相反了。unless they were rich，含义是“事实上他们不富有”，如果把unless改为if．．not，就变成“他们事实上是富有的”，意义恰好相反。可见在这种情况下，unless并不等于if．．not，而是相当于except on condition that，表示一种补叙。

I couldn't have got to Reykjavik in time unless I'd had a helicopter．

我当时不可能及时赶到雷克雅未克，除非我有直升飞机。

在这个句子中，unless也相当于except on condition that，从而也不能与if．．not交换。如果把原句改为．．if I hadn't had a helicopter，那就变成事实上有直升飞机了。

当unless不是作except on condition that解释时，即使表示非真实条件，unless与if．．not还是可以交替使用的。

I would have quit my job unless I had got a raise(=if I hadn't got a raise)．

要不是加到了工资，我早就辞职了。

They couldn't have afforded a vacation in Europe last summer unless they had borrowed money from the bank(=if they hadn't borrowed money from the bank)．

要不是向银行借了钱，去年夏天他们就无力去欧洲度假了。

I couldn't want to ask that boy to go to the dance with me unless I knew him(=if I didn't know him)．

要是我不认识那个小伙子，我不会请他和我一起去跳舞的。

Rufus was not the type to come to him unless it were something important(=if it were not something important)．

鲁弗斯这种人是不会来求他的，除非事情重要。

(2)用provided/providing(that)等引导。provided(that)=if，常用于正式语体。

Provided that you are here by 10，you can get in．

如果十点以前到这儿，你进得去。

He will write，provided that he is well．

要是身体好他会写信的。

提示：

在非正式语体中that往往省略。

Provided you sign the receipt，I will pay you the money．

如果你在收据上签个字，我就付你钱。

I will do anything you wish，provided it lies in my power．

我愿做任何你所希望的事，如果它是在我的权限以内。

providing(that)的用法与provided(that)基本相同。

He will play providing that the weather is good．

如果天气好，他会玩的。

I'll go providing it doesn't rain．

要是不下雨，我就去。

(3)条件状语从句还可用in case，assuming(that)，given(that)，so/as long as，supposing(that)，on condition that，with the proviso that，in the event that引导(这些用语除in case外，常见于正式语体)。

①用in case引导。

In case he comes，let me know．

如果他来的话，告诉我一声。

In case such a misfortune should befall us again，we must go to court．

如果再发生这种不幸的事情，我们必须起诉。

②用assuming(that)引导。

Assuming she gets to the store on time，we'll have a good dinner tonight．

她若按时到达商店，今晚我们就可以饱餐一顿了。

Assuming that he wants to get to London today，he must leave now．

若要今天抵达伦敦，他现在就得动身。

③用given(that)引导。

Given that the voters approve the fund，we'll have a new park in our town．

假使投票人通过拨款，我们城里就有一个新公园了。

Given that they are inexperienced，they have done a good job．

如果考虑到他们是一些生手，他们做得就算不错了。

④用so/as long as引导。

So long as the weather's fine，we'll have a picnic．

只要天气好，我们将举行野餐。

As long as you ask him beforehand，he won't object．

只要你事先问他，他是不会反对的。

⑤用supposing(that)引导。

Supposing that you run into difficulties in London，will the branch office there be able to help you?

假使你在伦敦遇到困难，那里的分公司能帮助你吗?

Supposing that the rain does not fall in a day or two，the young crops will be burnt up．

假使一两天内不下雨，幼苗就要枯焦了。

Supposing you had been more careful，such a calamity would not have befallen us．

如果你小心一些，我们就不会发生这种不幸的事情。

Supposing I were to have an accident，who would pay?

假使我出了事故，该由谁来赔偿?

⑥用on condition that，in the event that等引导。

They offered to go on condition that we supply food and drink．

他们提出的条件是，我们供应食品和饮料。

In the event that he refuses to sign the bond，what will happen?

如果他拒绝在契约上签字，会怎样呢?

In the event that the meeting is cancelled，I'll work on my report．

如果会议取消，我就写我的报告。

⑦用when或where引导。

When they resisted，they were killed．(人教大纲版高二下第47页)

他们如若抵抗便立即遭到屠杀。

Shylock，how can you hope for mercy yourself when you show none?(人教大纲版高二下第67页)

夏洛克，如果你对别人一点都不仁慈，你自己怎么能希望得到别人对你的仁慈呢?

A sports team can only function well when all team members cooperate．(人教大纲版高三第94页)

一个运动队只有在全体队员通力合作的情况下才能发挥得好。

Where the answer is yes，we intend to move forward．Where the answer is no，programs will end．(Obama's Inaugural Speech)

如果回答是肯定的，我们就要向前推进。如果答案是否定的，计划和项目就必须终止。