语态有两种：主动语态和被动语态。
主语是动作的发出者为主动语态；主语是动作的接受者为被动语态。
1）若宾语补足语是不带to 的不定式，变为被动语态时，该不定式前要加"to"。
此类动词为感官动词。
feel, hear, help, listen to, look at, make, observe, see, notice, watchThe teacher made me go out of the classroom.--> I was made to go out of the classroom (by the teacher).We saw him play football on the playground.--> He was seen to play football on the playground.2）情态动词+ be +过去分词，构成被动语态。
Coal can be used to produce electricity for agriculture and industry.let 的用法1）当let后只有一个单音节动词，变被动语态时，可用不带to 的不定式。
They let the strange go.---> The strange was let go.2）若let 后宾补较长时，let 通常不用被动语态，而用allow或permit 代替。
The nurse let me go to see my classmate in the hospital.----> I was allowed / permitted to see my classmate in the hospital.短语动词的被动语态短语动词是一个整体，不可丢掉后面的介词或副词。
This is a photo of the power station that has been set up in my hometown.My sister will be taken care of by Grandma.Such a thing has never been heard of before..表示"据说"或"相信" 的词组believe, consider, declare, expect, feel , report, say, see, suppose, think, understandIt is said that…据说It is reported that…据报道It is believed that…大家相信It is hoped that…大家希望It is well known that…众所周知It is thought that…大家认为It is suggested that…据建议It is taken granted that…被视为当然It has been decided that…大家决定It must be remember that…务必记住的是It is said that she will leave for Wuhan on Tuesday.不用被动语态的情况1) 不及物动词或动词短语无被动语态：appear, die disappear, end (vi. 结束), fail, happen, last, lie, remain, sit, spread, standbreak out, come true, fall asleep, keep silence, lose heart, take place.After the fire, very little remained of my house.比较： rise, fall, happen是不及物动词；raise, seat是及物动词。
