1、不定式作表语可以说明主语的具体内容或表示目的。
His wish is to become an astronaut.
他的愿望是成为一名宇航员。
What he hoped was to be admitted into the university.
他希望能被大学录取。
2、动词不定式作表语，常说明主语的内容、性质、特征。
The best way is to join an English club.
最好的办法是加入一个英语俱乐部。
The first thing is to listen to the teacher carefully.
首先是要认真听老师讲课。
注意：有些作表语的不定式，在结构上是主动的，但在意义上却是被动的。
She is to blame.
她应该受到责备。
The result is not long to see.
结果不久就会看到。
动词不定式的否定式
不定式的否定式是not / never to do...；不带to的不定式的否定式是not / never do...如：
1、They decide not to talk to each other.
他们决定不和彼此说话。
2、His parents tell him never to play soccer in the street.
他父母告诉他不要在街上踢足球。
不定式作表语表示具体动作或将来动作；动名词作表语表示抽象的一般行为。
①To be kind to the enemy is to be cruel to the people.
②My chief purpose is to point out the difficulties of the matter.
③What I would suggest is to put off the meeting.
当主语和表语都是不定式时，其含义一是条件，一是结果（例①）。当主语是aim,duty,hope,idea,mista ke,plan,purpose,suggestion等为中心词的名词词组（例②）时，或以what引导的名词性分句（例③），不定 式说明主语的内容。
④Our work is serving the people.
⑤What he likes is taking a walk after supper.
⑥The story told by Mr.Wang is interesting.
④⑤句动名词作表语，与主语部分可以转换，如Serving thepeople is our work,而⑥句中是现在分词作表语，说明主语的性质、状态，现在分词具有形容词的各种特征，另外，动名词作表语还应与进行时态区别开来。
