語態有兩種：主動語態和被動語態。
主語是動作的發出者為主動語態；主語是動作的接受者為被動語態。
1）若賓語補足語是不帶to 的不定式，變為被動語態 時，該不定式前要加"to"。此類動詞為感官動詞。
feel, hear, help, listen to, look at, make, observe, see, notice, watch
the 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）情態動詞+ be +過去分詞，構成被動語態。
coal can be used to produce electricity for agriculture and industry.
let 的用法
1）當let後只有一個單音節動詞，變被動語態時，可用不帶to 的不定式。
they let the strange go.---> the strange was let go.
2） 若let 後賓補較長時，let 通常不用被動語態，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.
短語動詞的被動語態
短語動詞是一個整體，不可丟掉後面的介詞或副詞。
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"據說"或"相信" 的詞組
believe, consider, declare, expect, feel , report, say, see, suppose, think, understand
it is said that… 據說
it is reported that… 據報導
it is believed that… 大家相信
it is hoped that… 大家希望
it is well known that… 眾所周知
it is thought that… 大家認為
it is suggested that… 據建議
it is taken granted that… 被視為當然
it has been decided that… 大家決定
it must be remember that…務必記住的是
it is said that she will leave for wuhan on tuesday.
不用被動語態的情況
1) 不及物動詞或動詞短語無被動語態：
appear, die disappear, end (vi. 結束), fail, happen, last, lie, remain, sit, spread, stand
break out, come true, fall asleep, keep silence, lose heart, take place.
after the fire, very little remained of my house.
比較： rise, fall, happen是不及物動詞；raise, seat是及物動詞。 (錯) the price has been risen.
(對) the price has risen.
(錯) the accident was happened last week.
(對) the accident happened last week.
(錯) the price has raised.
(對) the price has been raised.
(錯) please seat.
(對) please be seated.
要想正確地使用被動語態，就須注意哪些動詞是及物的，哪些是不及物的。特別是一詞多義的動詞往往有兩種用法。解決這一問題唯有在學習過程中多留意積累。
2) 不能用於被動語態的及物動詞或動詞短語：
fit, have, hold, marry, own, wish, cost, notice, watch agree with, arrive at / in, shake hands with, succeed in, suffer from, happen to, take part in, walk into, belong to
this key just fits the lock.
your story agrees with what had already been heard.
3) 系動詞無被動語態：
appear, be become, fall, feel, get, grow, keep, look, remain, seem, smell, sound, stay, taste, turn
it sounds good.
4) 帶同源賓語的及物動詞，反身代詞，相互代詞，不能用於被動語態：
die, death, dream, live, life
she dreamed a bad dream last night.
5) 當賓語是不定式時，很少用於被動語態。
(對) she likes to swim.
(錯) to swim is liked by her.
主動形式表示被動意義
1)wash, clean, cook, iron, look, cut, sell, read, wear, feel, draw, write, sell, drive…
the book sells well.這本書銷路好。
this knife cuts easily. 這刀子很好用。
2)blame, let(出租), remain, keep, rent, build
i was to blame for the accident.
much work remains.
3) 在need, require, want, worth (形容詞), deserve後的動名詞必須用主動形式。
the door needs repairing.= the door needs to be repaired.
this room needs cleaning. 這房間應該打掃一下。
this book is worth reading. 這本書值得一讀。
4) 特殊結構：make sb. heard / understood (使別人能聽見/理解自己)，have sth. done ( 要某人做某事)。
被動形式表示主動意義
be determined, be pleased, be graduated (from), be finished, be prepared (for), be occupied (in), get marries
he is graduated from a famous university.
他畢業於一所有名的大學。
注意： 表示同某人結婚，用marry sb. 或get married to sb. 都可。
he married a rich girl.
he got married to a rich girl.
need/want/require/worth
注意：當 need, want, require, worth(形容詞)後面接doing也可以表示被動。
your hair wants cutting. 你的頭髮該理了。
the floor requires washing. 地板需要衝洗。
the book is worth reading. 這本書值得一讀。
典型例題
the library needs___, but it'll have to wait until sunday.
a. cleaning b. be cleaned c. clean d. being cleaned
答案a. need (實意) +n /to do，need (情態)+ do，當為被動語態時，還可need + doing. 本題考最後一種用法，選a。如有to be clean 則也為正確答案。
典：done，"不可能已經"。must not do 不可以（用於一般現在時)。