2. if , unless，once引导的条件状语从句

e.g. If (it is) properly treated, waste will do no harm to the environment.

我不会去晚会的，除非我被邀请。

I'll not go to the party unless (I am) invited.

一旦你在超市里被抓到偷东西，你会受到惩罚的。

Once (you are) caught stealing in a supermarket, you will be punished.

3. though, although, whether, no matter whether/what/how/who等引导的让步状语从句

e.g. 他很开心，尽管他很贫穷。

He was happy, though/although (he was) poor.

他虽然年轻但懂得很多。

Though (he is) young, he knows a lot.

No matter how/However hard the task (is), we must fulfill it in time.

（注：从句的主语和主句的主语不一致时，只省略从句中的be动词形式）

4. as if, as though引导的方式状语从句

e.g. She lay there, as if (she was) dead. （省略的主语和主句的主语一致）

He opened his lips as if (he were going) to say something. 他张开嘴唇，好像要说什么话似的。

He stood up as if/though (he wanted) to leave.（as if/though + to do表示一个将来的动作）

二、than，as引导的比较状语从句中的省略用法：当不同的主语进行比较时，一般省略从句中的谓语；当从句中的主语与谓语（be动词除外）和主句中的主语与谓语相同时，通常省略从句中的主语和谓语，只保留比较部分。

e.g. He is taller than his brother (is).

I have as much as confidence in you as (I have confidence) in him.

三、以if从句为代表的状语从句中的特殊省略用法：通常省略了it is, that is, there is/are。

E.g.如果有必要的话，这个老庙会被重新修建。

If (it is) possible/necessary, this old temple will be rebuilt.

If (that is) so, I will call you back at 5:00 pm.

There are only a few books in our school library, if (there are) any.

四、定语从句中的省略用法

关系词的省略

关系代词that，which，whom等在限制性定语从句中充当宾语且不位于介词之后时，可以省略；in which或that在先行词way后作方式状语从句时可省略。

e.g. 你昨天拜访的那个人是我的祖父。

The man (that/who/whom) you visited last night is my grandpa.

我不喜欢你对待这个女孩的方式。

I don't like the way (in which/that) you treat the girl.

五、虚拟语气中if及should的省略

1. 当条件状语从句中有were, had, should等时省略if，把它们提至句首，形成倒装句。