一、一般现在时变否定句的规则.
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.
【例】This is a book. 否定句 This is not a book .
I am a teacher . 否定句I am not a teacher .
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。
【例】He eats an apple. 否定句 He doesn't eat an apple.
Jim does his homework. 否定句 Jim doesn't do his homework.
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】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.
【例】 I can dance. 否定句 I can not dance. 或 I can't dance.
They can speak English. 否定句 They can not speak English. 或They can't speak English.
【注意】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 mecting.否定句 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。
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.
四)、注意
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
not have或doesn’t have (has要变成have)