及物动词：本身意思不完整，需要接宾语才能使其意思完整的动词。如：Tom loves music. 汤姆喜欢音乐。
不及物动词：自身意思已完整，无须接宾语的动词。如：The sun rises from the east. 太阳从东方升起。
在英语语法书和中学英语教科书中，一般对及物动词和不及物动词只作了简单的解释，即需要跟宾语的动词叫及物动词，不需要跟宾语的动词叫不及物动词。但是，在实际运用中，有一些及物动词后面又不允许带有宾语。故初学者对错句The box is too heavy to carry it. 的it为什么要去掉才是正确的，他们不知道其理由。那么，究竟在什么情况下，及物动词才用作不及物动词呢？本文就谈谈笔者的一点见解，同大家探讨。
1. May I smoke?
May I smoke a cigarette?
2. I wrote to my penfriend.
I wrote a letter / an email etc. to my penfriend.
3. Help me wash up.
Help me wash up dishes.
4. The Greens always ate at the stone table.
The Greens ate all their meals at the stone table.
5. He always reads in the morning.
He always reads newspapers in the morning.
6. I don't drink.
I don't drink alcohol.
1. We wash ourselves before breakfast.
We wash before breakfast.
2. The boy hid himself behind the door.
The boy hid behind the door.
3. Tom dressed himself quickly and went downstairs.
Tom dressed quickly and went downstairs.
4.I always shave myself before breakfast.
I always shave before breakfast.
但：①Make yourself at home.
不能说：Make at home.
②Help yourself to some fish.
不能说：Help to some fish.
③The boy cut himself just now.
不能说：The boy cut just now.
1. The stone is very heavy. I can t lift it.
The stone is too heavy for me to lift.
2. They read the novel with great interest.
The novel is interesting for them to read.
3. Look at the new watch. How nice it is!
The new watch is nice to look at.
1. I decided to mend the shoes.
There are some shoes to mend.
2. It is difficult for you to teach the boy.
He is a difficult boy for you to teach.
3. We are looking after five blind children.
We have five blind children to look after.
1. We must dismiss those who are not fit for their offices.
Those who are unfit for the offices they hold are to be dismissed.
2. You should decide it by yourself.
It is for you to decide.
3. They often blame their tools.
No one is to blame for it.
1. We want to look after the children.
The children wants looking after.
2. I stopped winding my watch and started to work.
The watch needs winding up.
3. I hate thinking it over.
The problem requires thinking over.
4. It is the fine morality of the Chinese people cherishing the young and respecting the old.
The old deserve respecting.
1. It is worth while reading the book.
The book is worth reading.
2. It is difficult for us to teach Tom.
Tom is not worth teaching.
3. Did he make ready for solving the problem?
This problem is beyond his solving.