一般现在时怎样变否定句
一、主语＋be动词
含有 am is are 的句子,变否定句时,只需在am is are 后加not.
1、 This is a book. 否定句 This is not a book.
2、 I am a teacher. 否定句I am not a teacher.
3、 These are pens. 否定句These are not pens.
二、主语＋实义动词
含有实义动词的句子，变否定句分两种。
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。
He eats an apple. 否定句 He doesn't eat an apple.
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.
I teach English. 否定句 I don't teach English.
三、主语＋情态动词
含有情态动词的句子,变否定句时, 只需在情态动词后加not.
1、 I can dance. 否定句 I can not dance. 或 I can't dance.
2、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.
You must say something at the meeting.
扩展资料
注意点：
1、含有have和has的句子变成否定句
have和has，变否定句不能在have和has后加not，则需要助动词来帮助解决。
have→do not have或don’t have
has→does
2、见到some 变否定句时,要换成any.
I eat some apples. 否定句 I don't eat any apples.
3、见到and 变否定句时,要换成or.
There is some air and water on the moon.
否定句 There isn't any air or water on the moon.
4、见到too和also变否定句时,要换成either.
too和also用于肯定句中时，否定句中用either替换。
Tom goes to school too.
否定句 Tom doesn’t go to school either.
5、a lot of (=lots of)变为many或much。
They have a lot of friends.（可数名词）
否定句They don't have many friends.
6、见到already变否定句时,要换成yet。
He has had supper already.
否定句 He hasn’t had supper yet.
(a) 含有 am is are 的句子,变否定句时,只需在am is are 后加not.
例：This is a book.
否定句：This is not a book .
(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:He eats an apple.
否定句:He doesn't eat an apple.
(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:I teach English.
否定句 I don't teach English.
(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:I can dance.
否定句 I can not dance.
或 I can't dance.
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:You 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：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： 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： I eat some apples.
否定句 I don't eat any apples.
(2) 见到and 变否定句时,要换成or.
例：There is some air and water on the moon.
否定句 There isn't any air or water on the moon.
(3) 见到too和also变否定句时,要换成either.
例: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: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.把动词后面＋s即可
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