6-1 否定句的基本规则
在任何语言，我们都有必要造出〝否定〞的句子，在中文，写出否定句子并非难事，在英文，无论任何否定句子，都必须遵行一些规定，以下是否定句子的例子
肯定句子
I like music.
He loves swimming.
They have come to work.
Mary went to see a movie yesterday.
John is a good boy.
I will go to New York tomorrow.
He can sing.
You may go now.
He should sleep early.
It is raining now.
It rains very often here.
He has a lot of money.
It is exciting to see this game.
He asked me three questions.
否定句子
I don’t like music.
He does not love swimming.
They have not come to work.
Mary did not go to see a movie yesterday.
John is not a good boy.
I will not go to New York tomorrow.
He can not sing.
You may not go now.
He should not sleep early.
It is not raining now.
It does not rain very often here.
He does not have a lot of money.
It is not exciting to see this game.
He did not ask me three questions.
从以上的例子来看，我们可以归纳出以下的规则：
1.Verb to be 后面可以直接加not。例如：
He is not a good teacher.
Mary was not very happy when she was young.
They are not strong boys.
Peter is not coming.
John is not going to work.
2.助动词后面可以直接加not。例如：
He has not written any letter.
They will not come.
He cannot swim.
They should not cry very often.
Tom had not eaten any thing before you came.
He may never eat cakes in the future.
John has not lived here.
3.一般句子的动词必须加入do或他的变形。
He does not smoke.
He did not go.
I do not love sports.
You do not like to eat fish.
They do not swim very well.
We did not see that movie.
在英文中，我们可以用have to来代替must，以下是have to的例子：
He has to go to Chicago tomorrow.(他明天应该去芝加哥)
They had to buy three tickets to go to the concert.(他们必须买三张票去听音乐会)
I have to work very hard.(我必须努力工作)
含有have to的句子，如要改成否定句子，必须在have to前面加do或它的变形，请看以下的例子：
肯定句子
He has to eat a lot of food.
He had to leave.
I have to write that letter.
否定句子
He does not have to eat a lot of food.
He did not have to leave.
I do not have to write that letter.
