Unless 的用法

1、unless所引导的条件状语从句常用一般现在时表示将来意义,主句多用一般将来时。

2、unless在表示“除非”时,如其引导的从句谓语是be,而从句的主语跟主句的主语相同时,从句的主语和be就可省略。有时从句中主语为it时,也可省略it或从句中的有关成分。

3、在unless引导的肯定形式的条件从句中通常用肯定词,如:already, still, some, too。在unless引导的否定形式的条件从句中通常用否定词。

状语从句的省略如下：

1.当状语从句的主语是it,且谓语动词是be时，it和be要完全简化掉。

If (it is) possible, he will help you out of the difficulty.

如果可能的话，他会帮你摆脱困境。

He’ll go to the seaside for his holiday if (it is ) possible.

如果可能的话，他将去海边度假。

Phone me if (it is) necessary. 必要时给我打电话。

If ( it is ) necessary, I will come to see you off tomorrow.

如果有必要，我明天来送你。

If (it is) possible, he will help you out of the difficulty.

如果可能的话,他会帮你摆脱困境。

You must attend the meeting unless (it is) inconvenient to you.

除非情况对你来说不方便,否则你必须出席这次会议。

Fill in the application as (it is) instructed. 按照要求填好表格。

As (it is) scheduled they met on January 20. 他们按照计划在1月20日碰头。

2.状语从句是there be句型时，则there be可省略。

Correct the mistakes in the following sentences if any (=if there is any)

如果有错要对有错误的句子进行订正。

There is few if (there is) any. 如果有也很少。

3.当状语从句的主语和主句的主语一致时，从句可以将主语和be动词简化掉。

Start when (you are) ready. 准备好了就开始。

He danced about as if (he was) in search of something. 他向四周望望，仿佛在找什么似的。

As (he was) young, he learned how to ride a bike.

他小时候就学会了骑自行车。

Once （The film is ）exposed to light, the film will be damaged and get useless. 一旦曝光，胶卷就要被损坏而不能用了。

Although (the engine is) built before the war, the engine is still in perfect order.

尽管是战前制造的，这台发动机仍然处于良好状态。

Although (he was) a farmer, now he is a famous director.

尽管他曾是个农民,而现在是位著名的导演了。

Although (he is) doing his best in maths these days, he has still got no good marks.

尽管近来他一直在学数学,但他仍然没有取得好成绩。

He won't go there with us unless (he is) invited.

除非受到邀请,否则他不会和我们一道去那里。

The concert was a great success than (it was) expected.

这场音乐会出乎意料地取得了巨大成功。

He stood up as if (he were) to say something.

当时他站起来好像要说什么。

He wouldn't solve the problem even if (he were) to take charge.

即使他来负责,他也解决不了这个问题。

She looked anxious as though (she was) in trouble.

她看上去很焦急,好像遇到了麻烦。

He had mastered the English language before (he was) in the USA.

他到美国之前就懂英语了。

The law could arrest the development of good research if (the law were ) applied prematurely.

如果草率施行，该法律将会阻滞高质量研究的进展。

Unless (this law is ) changed, this law will make life difficult for farmers.

除非加以修改，否则这条法律将给农民的生活造成困难。

When (the boy was ) asked why he came here, the boy kept silent.

当那个男孩被问到为何来这里时，他沉默不语。

When (these skills are) learned early on, these skills can be used throughout their college education.

这些技能虽在早期学习的，但这些技能可以在整个大学教育中都能使用。

As (he was) young, he learned how to ride a bike.

他小时候就学会了骑自行车。

Work hard when (you are) young, or you'll regret.

少壮不努力,老大徒伤悲。

4. 比较状语从句经常省略。

The higher the temperature (is), the greater the pressure (is ).

温度越高，则压力越大。

I know you better than he (does). 我比他更了解你。

He is as quick in answering as his sister (is). 他回答得和他妹妹一样快。

He answers as quickly as his sister (does). 他回答得和他妹妹一样快。

He is not so / as quick in answering as his sister (is). 他回答得不如他妹妹那样快。

His sister is quicker than he (is). 他妹妹比他敏捷。

He moves more slowly than his sister (does). 他行动起来比他妹妹慢。

结果状语从句省略that

so that, so…that, such…that 引导结果状语从句时，有时可省略that。

He was so drunk (that) he could barely stand. 他喝醉了，勉强能站立。

The girls are so close (that) they're like sisters. 女孩们亲如姐妹。

There was such a lot of rain (that) we couldn't go out. 雨那么大，我们没法出去。

She spoke with such sincerity (that) he felt greatly touched. 她说得那样诚恳，他深受感动。

such/so...that引导结果状语从句，为了强调，还可以将主句中的so或such引导的部分置于句首从而构成倒装结构。请看例句：

so fast does that light travel that it difficult for us to imagine its speed.

正常语序为：

light travels so fast that it is difficult for us to imagine its speed.

光的传播速度是如此之快，以至于我们无法想象它的速度。

小结：

状语从句的省略是指使语言的精炼将状语从句进行简化。需满足两个条件: 主句和从句的主语一致，或从句主语为it；从句谓语动词一般是be的某种形式。但没有be也是可以的：

When I walked across the bridge, I found a boy sitting under a tree.

可以省略为：

When walked across the bridge, I found a boy sitting under a tree.

When walking across the bridge, I found a boy sitting under a tree.

Walking across the bridge, I found a boy sitting under a tree.

当我走过桥时，我发现一个男孩坐在树下。

注意:当从句主语和主句主语不一致时,从句部分要么用完全形式,要么用独立主格结构来表达。例如:

When the meeting was over, all the people went out of the meeting-room.

当会议结束时,人们都走出了会议室。