一、省略主语和动词be
当状语从句的主语与主句主语一致，且从句谓语包括有动词be时，有时可省略从句中的主语和动词be。如：
Phone me if (it is) necessary. 必要时给我打电话。
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。
Though (he was) intelligent, he was very poorly educated. 虽然他很聪明，受的教育却很差。
注：有时省略的可能是 there is, it is 等。如：
There is few if (there is) any. 如果有也很少。
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。
二、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。如：
I am so busy (that) I have no time to write a letter. 我是那样忙，写信的时间都没有。
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。
三、比较状语从句的省略
as, than等引出的比较大状语从句通常省略谓语。如：
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。
