变否认句规则一、一般现在时变否认句的规则.(a) 具有 am is are 的句子,变否认句时,只需在am is are 后加not. 例1 This is a book. 否认句 This is not a book . 例2 I am a teacher . 否认句I am not a teacher . 例3 These are pens . 否认句These are not pens .(b) 具有实义动词的句子，变否认句分两步。 （1）假如主语是第三人称单数时，要在实义动词前加doesnt,后面的动词用原形。 例1 He eats an apple. 否认句 He doesnt eat an apple. 例2 Jim does his homework. 否认句 Jim doesnt do his homework. 例3 Marry goes to school. 否认句Marry doesnt go to school. (2) 假如主语不是第三人称单数时，只需在实义动词前加dont. 例1 I teach English. 否认句 I dont teach English. 例2 They go to school. 否认句 They dont go to school. 例3 We sing a song. 否认句 We dont sing a song. (c) 具有情态动词的句子,变否认句时,只需在情态动词后加not. 例1 I can dance. 否认句 I can not dance.或 I cant dance. 例2 They can speak English. 否认句 They can not speak English. 或 They cant speak English. 例3 He must go home. 否认句 He must not go home. 或 He mustnt go home. 例4 He must be on the playground. He can not be on the playground. 析：当must be用来表达推测，有“一定”的含义时， 否认式要用can not. 例5You must say something at the mecting. You neednt say anything at the mecting. 析：当“must+行为动词”用来表达“必须”的含义时， 其否认式可用neednt 或mustnt表达“不需要”，“不必”， 语气委婉，must not表达“严禁”，“千万别”语气生硬。 例6 You may come in now. You mustnt come in now. 析：may作为情态动词表达“可以”时，其否认式用must not,而不用may not. 例7 He may watch TV . He mustnt watch TV. 注意: (1) 见到some 变否认句时,要换成any. 例1 I eat some apples. 否认句 I dont eat any apples. 例2 He has some books. 否认句 He doesnt have any books.例3 He does his home work. 否认句 He doesnt do his home work. (2) 见到and 变否认句时,要换成or. 例1 There is some air and water on the moon. 否认句 There isnt any air or water on the moon. 例2 He has some brothers and sisters. 否认句 He hasnt any brothers or sisters. 例3 He eats apples and oranges. 否认句He doesnt eat apples or oranges. (3) 见到too和also变否认句时,要换成either. 例1. Tom goes to school too. 否认句 Tom doesnt go to school either. too和also用于肯定句中时，否认句中用either替换。 （4）见到already变否认句时,要换成yet。 例1 He has had supper already. He hasnt had supper yet. 随着对谓语动词的否认，某些副词也要作相应的变动。 英语句型转换错误分析：肯定句变否认句 1. I think she is there. 误：I think she isnt there. 正：I dont think she is there. 析：英语中think, believe, expect, suppose等表达信念和揣测的动词， 后接that从句时，习惯上将从句中的否认形式转移到主句上， 即否认主句谓语，不否认从句谓语。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在否认句中一般要改为or。3. Tom went to school too. 误：Tom didnt go to school too. 正：Tom didnt go to school either. 析：too和also用于肯定句中时，否认句中用either替换。4. He has had supper already. 误：He hasnt had supper already. 正：He hasnt had supper yet. 析：随着对谓语动词的否认，某些副词也要作相应的变动。 5. He had a good rest just now. 误：He hadnt a good rest just now. 正：He didnt have a good rest just now. 析：have在表达开会、吃饭、休息、进行体育锻炼等词组中是行为动词， 否认句用助动词来完毕。 6. Lets do it. 误：Lets dont do it. 正：Dont lets do it.或Lets not do it. 析：let后接的是不带to的不定式，变为否认式， 直接在句首前加Dont或在不定式前加not。7. He always gets there on time. 误：He doesnt always get there on time. 正：He never gets there on time. 析：He doesnt always get there on time意为 “他并非老是准时到那儿”，是部分否认， 习惯上把句中的副词改为相应的表达否认的副词即可。如： It often rains here. It seldom rains here.8. Be here early tomorrow. 误：Be not here early tomorrow. 正：Dont be here early tomorrow. 析：祈使句的否认，一般