一、语态概述
语态是动词的一种形式,表示句子之中主语和谓语动词的关系.英语有两种语态：主动语态和被动语态
主动语态表示主语是动作的发出者（或执行者）eg：Many people speak Chinese.谓语：speak的动作是由主语many people来执行的.
被动语态表示主语是动作的承受者,即行为动作的对象.eg：Chinese is spoken by many people.主语English是动词speak的承受者.
二、被动语态的构成
被动语态由助动词be＋及物动词的过去分词构成.人称、数和时态的变化是通过be的变化表现出来的.(被动语态的否定式和疑问式均由助动词或第一个助动词构成.)
各种时态的被动语态构成：
1.一般现在时：am/is/are＋及物动词的过去分词
I'm asked to take care of myself. Football is played all over the world
2.一般过去时：was/were＋及物动词的过去分词
This house was built in 1958. His leg was broken in an accident.
3.一般将来时：will/shall be＋及物动词的过去分词
More factories will be built in our city. He will be taken to hospital tomorrow.
4.现在进行时：am/is/are being＋及物动词的过去分词.
A road is being built around the mountain. Many new houses are being built in this city
5.过去进行时：was/were being＋及物动词的过去分词
he meeting was being held when I was there. We were being trained this time last year.
6.现在完成时：have/has been＋及物动词的过去分词
His book has been translated into many foreign languages. The prices of many goods have been cut again .
7.过去完成时：had been + 及物动词的过去分词
A new school had been set up by the end of last year.
8.含有情态动词的被动语态：情态动词+be+及物动词的过去分词
The rubbish can be put into the dustbin over there.
三、被动语态的基本用法
一般来说,在我们日常生活中,能用主动语态的时候就尽量不去用被动语态.只有在下列情况中我们才用被动语态：1.不知道动作的执行者是谁.
1).Some new computers were stolen last night.一些新电脑在昨晚被盗了.
2).This bridge was founded in 1981.这座桥竣工于1981年.
3).The front window in the classroom was broken yesterday. 昨天,教室的前窗被打
2.没不要说出动作的执行者是谁.
1).The time-table has been changed .时间表已变动了
2).China was founded in 1949.
3.不愿意说出动作的执行者,其目的是为了使语言得体、圆滑等.在这种情况下,有时常用一些句式,如It is said that…（据说……）,It is reported that …（据报道）,It is well known that（众所周知……）It is supposed that（据推测说, It is believed that…大家相信,It is hoped that…大家希望,It is thought that…大家认为,It is suggested that…据建议等等.
It is said that she is going to be married to a foreigner.据说她要嫁给一个外国人.
It is said that the boy has passed the national exam. （＝The boy is said to have passed the national exam.）
4.强调动作的承受者,而不强调动作的执行者.
1).The glass was broken by Mike.玻璃杯是迈克打破的.
2).his book was written by him.这本书是他写的.
3).Your homework must be finished on time.你们的家庭作业必须及时完成.
注：使用被动语态的情况口诀：动作谁做的不知道,谁说出的不必要.接受动作需强调,用被动语态最为妙.
四、主动语态变被动语态的方法：
1.把主动语态的宾语变为被动语态的主语.
2.把谓语变成被动结构(be＋过去分词) (根据被动语态句子里的主语的人称和数,以及原来主动语态句子中动词的时态来决定be的形式).
3.把主动语态中的主语放在介词by之后作宾语,将主格改为宾格.
He plant trees in spring.
Trees are planted in spring by him.
主动语态变被动语态口诀：宾语提前主语变,原主变宾by后见,时态人称be关键.
All the people laughed at him. →He was laughed at by all people.
They make the bikes in the factory.→The bikes are made by them in the factory.
He cut down a tree. → A tree was cut down by him.
被动语态中by+宾语的省略：
被动语态句式中的by+宾语表示及物动词所表示动作的执行者,但是在遇到以下情况时,表示动作执行者by+宾语常常被省略.
动作执行者不确定时
Paper is made from wood.
Many people are killed in traffic accidents every day .
不必表明动作执行者时
English is also spoken as the second language as well as one of the official languages.
Football is played in most school.
动作执行者为一般大众时.
Both English and Spanish are spoken in this area.
He is made the monitor of the class today.
五、主动语态变被动语态应注意的几个问题：
谈谈几种特殊的被动结构
1.当句子结构为主语+谓语+宾语（唯一宾语）时,把宾语提到句首做主语,然后把谓语改成被动语态形式,最后把原主语变为宾格至于介词by之后.实际运用中by短语常被省略.
We finish our homework in the evening.
Our homework is finished in the evening.
2. 当句子结构为主语+谓语+间接宾语(表示人的)+直接宾语（表示物的）时,一般把间接宾语变为主语,而直接宾语不变,这样句子显得自然些.如果把直接宾语作为主语,那么在间接宾语前应加介词to或for.
She sent me a novel on my birthday. (主动) →
I was sent a novel on my birthday. (被动)
A novel was sent to me on my birthday. (被动)
My brother bought me a watch yesterday. (主动) →
I was bought a watch yesterday. (被动)
A watch was bought for me by my brother yesterday.(被动)
注意：
1).间接宾语前需要加for的动词buy ,sing ,catch ,find ,get,drow ,cook ,keep ,make,offer 等.
2).间接宾语前需要加to的动词bring ,give ,pass ,hand ,leave ,show ,write ,take ,teach ,tell ,thow ,lend,send ,return等
3).当句子结构为主语+谓语+宾语+宾语补足语把主动态变成被动态时,只需将主动语态的宾语变为被动语态句子的主语,而原句里的宾语补足语现在就变成被动态句子的主语补足语了
They asked me to help them. →I was asked to help them.
Now people can use computers to help them →.Computers can be used to help them.
We must keep the room clean. →The room must be kept clean .
We saw them coming over. →They were seen coming over.
如果复合宾语是由宾语+不带to的动词不定式构成,变为被动语态时,动词不定式前的to要补出来.常见的这类动词有：一感（feel）,二听（hear,listen to ）三让（let ,make ,have ）四看（watch ,see ,notice ,observe,+look at ）但动词为let时,to仍可省略.
The story made us laugh. →We were made to laugh by the story.
The teacher let the little boy go home. →The little boy was let (to) go home .
4).含有情态动词的被动语态
含有情态动词的主动语态变成被动语态时,由情态动词＋be＋过去分词构成,原来带to的情态动词变成被动语态后to仍要保留.
