.
变否定句规则
一、一般现在时变否定句的规则.
(a) 含有am is are 的句子,变否定句时, 只需在am is are 后加not.
例1 This is a book.
否定句This is not a book .
例2 I am a teacher .
否定句I am not a teacher .
例3 These are pens .
否定句These are not pens .
(b) 含有实义动词的句子，变否定句分两步。
（1）如果主语是第三人称单数时，要在实义动词前加doesn't,后面的动词用原形。
例1 He eats an apple.
否定句He doesn't eat an apple.
例2 Jim does his homework.
否定句Jim doesn't do his homework.
例3 Marry goes to school.
否定句Marry doesn't go to school.
(2) 如果主语不是第三人称单数时，只需在实义动词前加don't.
例1 I teach English.
否定句I don't teach English.
例2 They go to school.
否定句They don't go to school.
例3 We sing a song. 否定句We don't sing a song.
(c) 含有情态动词的句子,变否定句时,只需在情态动词后加not.
例1 I can dance.
否定句I can not dance. 或I can't dance.
例2 They can speak English.
否定句They can not speak English. 或They can't speak English.
例3 He must go home.
否定句He must not go home. 或He mustn't go home.
.
例4 He must be on the playground.
He can not be on the playground.
析：当must be用来表示推测，有“一定”的含义时，
否定式要用can not.
例5You must say something at the mecting.
You needn’t say anything at the mecting.
析：当“must+行为动词”用来表示“必须”的含义时，
其否定式可用needn’t 或mustn't表示“不需要”，“不必”，
语气委婉，must not表示“禁止”，“千万别”语气生硬。
例6 You may come in now.
You mustn't come in now.
析：may作为情态动词表示“可以”时，其否定式用must not,而不用may not.
例7 He may watch TV .
He mustn't watch TV.
注意:
(1) 见到some 变否定句时,要换成any.
例1 I eat some apples.
否定句I don't eat any apples.
例2 He has some books.
否定句He doesn't have any books.
例3 He does his home work.
否定句He doesn't do his home work.
(2) 见到and 变否定句时,要换成or.
例1 There is some air and water on the moon.
否定句There isn't any air or water on the moon.
例2 He has some brothers and sisters.
否定句He hasn't any brothers or sisters.
例3 He eats apples and oranges.
否定句He doesn’t eat apples or oranges.
(3) 见到too和also变否定句时,要换成either.
例1. Tom goes to school too.
否定句Tom doesn’t go to school either.
too和also用于肯定句中时，否定句中用either替换。
（4）见到already变否定句时,要换成yet。
例1 He has had supper already.
He hasn’t had supper yet.
随着对谓语动词的否定，某些副词也要作相应的变动。
英语句型转换错误分析：肯定句变否定句
1. I think she is there.
误：I think she isn’t there.
正：I don’t think she is there.
析：英语中think, believe, expect, suppose等表示信念和揣测的动词，
后接that从句时，习惯上将从句中的否定形式转移到主句上，
即否定主句谓语，不否定从句谓语。
2. He can sing this song and that one.
误：He can not sing this song and that one.
正；He can not sing this song or that one.
析：肯定句中的连词and在否定句中一般要改为or。
3. Tom went to school too.
误：Tom didn’t go to school too.
正：Tom didn’t go to school either.
析：too和also用于肯定句中时，否定句中用either替换。
4. He has had supper already.
误：He hasn’t had supper alre ady.
正：He hasn’t had supper yet.
析：随着对谓语动词的否定，某些副词也要作相应的变动。
5. He had a good rest just now.
误：He hadn’t a good rest just now.
正：He didn’t have a good rest just now.
析：have在表示开会、吃饭、休息、进行体育锻炼等词组中是行为动词，
