如题所述
不定式是由不定式符号to动词原形构成。不定式具有动词的特征，同时也有名词、形容词和副词的特征。动词不定式在句中可以作主语、宾语、表语、定语和状语，还可用在复合结构中，而且有完成式、进行式、完成进行式和否定形式。何时用不定式呢？
1） 带to的动词不定式作宾语的动词主要有：要求选择同意(ask, choose, agree)，期望决定学习(expect, hope, decide, learn)，宁可假装知道(prefer, pretend, know)，希望想要愿意(wish, want, would like / love)。如
I ask him to answer the question.
I agree to attend the meeting.
I prefer to take that blue one.
I would like to have a dinner with you.
2) 用不定式修饰抽象名词 (ability, chance, idea, excuse, promise, 等 ）如
a / the ability to do sth ，“做某事的能力”
It is a good idea to deal with the problem.
This is a chance for you to leave there.
3) 不定式修饰被序数词, 最高级, no, any, all 所限定的中心词： 如
He is always the first man to enter the classroom.
He is the first one to believe me.
He was the best man to do the job.
4) 用不定式表将来的目的性行为 ： 如
I borrowed some books to read during my holiday.
5) 句型：如
It’s time to do sth.
It takes sb. some time to do sth.
It’s+adj.+ for（of） sb. to do sth.
1） 带to的动词不定式作宾语的动词主要有：要求选择同意(ask, choose, agree)，期望决定学习(expect, hope, decide, learn)，宁可假装知道(prefer, pretend, know)，希望想要愿意(wish, want, would like / love)。如
I ask him to answer the question.
I agree to attend the meeting.
I prefer to take that blue one.
I would like to have a dinner with you.
2) 用不定式修饰抽象名词 (ability, chance, idea, excuse, promise, 等 ）如
a / the ability to do sth ，“做某事的能力”
It is a good idea to deal with the problem.
This is a chance for you to leave there.
3) 不定式修饰被序数词, 最高级, no, any, all 所限定的中心词： 如
He is always the first man to enter the classroom.
He is the first one to believe me.
He was the best man to do the job.
4) 用不定式表将来的目的性行为 ： 如
I borrowed some books to read during my holiday.
5) 句型：如
It’s time to do sth.
It takes sb. some time to do sth.
It’s+adj.+ for（of） sb. to do sth.
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