大家都知道，英语在人们生活中的重要性，可是即使如此，大家在学习英语的过程也都会遇到各种各样的问题，其中关于语法的问题是最为严重的，因为即使你知道单词怎么写，即使你知道怎么念，可是因为语法的错误也一样会闹出笑话，今天沪江的小编就在这里给大家整理了一般现在时讲解：否定句的结构，仅供参考。

　　一般现在时的否定句

　　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)

　　【例】I have a pen. 否定句I don’t have a pen。

　　My father has a watch. 否定句 My father doesn't have a watch.

　　2、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.

　　He has some books. 否定句 He doesn't have any books.

　　He does his home work. 否定句 He doesn't do his home work.

　　3、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.

　　He has some brothers and sisters.

　　否定句 He hasn't any brothers or sisters.

　　He eats apples and oranges.

　　否定句He doesn’t eat apples or oranges.

　　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。

　　【例】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。

　　【例】They have a lot of friends.(可数名词)

　　否定句They don't have many friends.

　　There is lots of orange in the bottle.(不可数名词)

　　否定句There isn't much orange in the bottle.

　　6、见到already变否定句时,要换成yet。

　　【例】He has had supper already.

　　否定句 He hasn’t had supper yet.

　　以上就是沪江的小编为大家整理的一般现在时的否定句结构，这只是英语众多语法中的一个，不过只要掌握了这个语法，在之后做题的过程中也就会顺利很多，如果还有其他方面的语法问题，大家可以上沪江网进行咨询，也可以报名英语语法相关的课程。