英语句子的基本结构(2)
英语文法的规则(5)：在不定词“to”的后面，必须用原形动词
英文中的动词，是会变化的，以have为例，第一人称和第三人就不同：
I have a dog.
He has a dog.
如果是过去式，动词又要变化。have的过去式是had，不论第几人称，一概都要用had。几乎每一个英文动词的过去式都有变化，以下是几个例子：
go went come came eat ate play played swim swam
不论那一个动词，都有一个原形动词，一切都是从这个原形动词变出来的，像go、drink、have、walk、love、like等等都是原形动词。
如果我们有必要要用不定词to，就必须用原形动词，例如to go、to drink、to have，都是正确的，*to went;*to drank;*to loved等等都是错的。
英文中有一个动词最为麻烦，那就是am、are、is、was、were等等，翻译成中文，这都是，而这些动词的来源都是be，所以我们说这些动词都是verb to be。
以下的句子都用上了〝be〞
I want to be a teacher.
He wants to be a good father.
They all love to be rich.
No one likes to be poor.
英语文法的规则(6)：英文中有所谓的助动词。必须注意
英文中有很多动词都是助动词，在规则(4)中，我们说在绝大多数的否定语句中，必须用助动词do或did。Do是原形动词，did 和does都是do的变形。
除了do是助动词以外，can、may、might、will、would、must也都是助动词。
以上所提到的助动词，都有一个共同的特色，那就是这些助动词后的动词必须是原形动词，以下的句子都是正确的：
He can swim.
He does not swim.
I do not speak English.
You must walk to work every day.
I did not work yesterday.
You may leave now.
I will go to Taipei tomorrow.
以下的句子都是错的：
* I did not went.
* He does not goes to work.
* You must walked to work.
除了以上的助动词以外，还有一个非常特殊的助动词，那就是have，在这个助动词的后面，动词绝对不能用原形动词，以下是用这个助动词的例子：
I have been to England.
I have slept all day.
I have studied English since I was a child.
been、slept 和studied都是过去分词(past participle)，以下的句子也都是现在完成式，我们后讨论完成式的时候，会将这些解释清楚的。
英语文法的规则(7)：英文问句要有助动词
我们先看看以下的英文句子，这些都是错的：
* How many books you wrote?
* How many sons you have?
正确的句子是：
Why do you drink so much water?
How many books did you write?
How many sons do you have?
绝大多数的英文问句子是一定要有助动词，以下全是正确的英文问句，你可以看出每一句的助动词吗?
Do you love me?
Did you go to school yesterday?
How many books do you have?
How much money does he have?
Why don't you go back home?
Do you like to swim?
Can you play violin?
Will you go home tomorrow?
Would you give me a call?
当然啦，一旦动词是verb to be，我们又不需要助动词了，以下都是正确的英文问句：
Are you a teacher?
Is he a student?
Is Mr. Chang your father?
Were your mother and father in England last year?