⒌ 作宾补

通常用于advise, allow, ask, beg, cause, challenge, convince, enable, encourage, expect, forbid, force, instruct, invite, order, permit, persuade, recommend, remind, request, require, teach, tell, train, urge, want, warn等词后。

如：He ordered her to leave at once.

He was forced to obey his mother's order.

⒍ 作状语

不定式作状语时通常表示目的，不定式用作目的状语有两个可能的位置，一是在句首，二是在句末。一般说来，用于句首属于强调性用法，即强调动词的目的。也可用于"be adj. to do"结构中作原因状语。

如：He got up early to catch the first bus.

To finish the task on time, we have to work hard.

I'm happy to hear the news.

I'm surprised to see him here.

only to...往往表示"意想不到"的结果；never to...可以接后续的结果。so...as to..., such... as to..., enough to..., only to...以及too...to...等结构中的不定式也表结果：

如：Her father disappeared, never to be heard again.

I went to the bank only to find it was closed.

不定式和现在分词作状语的区别

⒈ 作目的状语。不定式作目的状语，带有很强的目的性，有时可以把(in order) to do置于句首。而现在分词作目的状语时，目的和伴随兼而有之。多放于句末，与主句用逗号隔开。

如：(In order) to ensure success, we must make a complete and through plan.

You should keep it a secret, trying to protect the plan.

⒉ 作结果状语。不定式作结果状语表示意外的结果。现在分词作状语表示自然的结果。

如：He returned home many years later, only to find that everything had changed.(意外的结果)

It rained heavily last night, causing the river to rise.(自然的结果)

⒊ 作独立成分

to be honest, to begin with, to start with, to tell you the truth, to make a long story short

如：To tell you the truth, I told a lie.

To begin/start with, let's sing a song.

To make a long story short, he succeeded in passing the exam.

不定式特殊用法

⒈ 用it作形式主语

动词不定式作主语时，如果主语太长，通常用it作形式主语，将真正的主语--动词不