不定式有六种形式，以 write 为例，列表如下：
to be written
to have written
to have been written
to be writing
to have been writing
He seems to know this.
He pretended to be working hard.＝He pretended that he was working hard.
When he came in, I happened to be reading the novel.
I am sorry to have given you so much trouble.
She is said to have just completed a novel.
The rain was said to have been falling for a week.
He was happy to have been staying with his uncle.
She felt puzzled to be asked such a question.
The factory to be built here next year is a car factory.
The weather will be sunny in the days to come.
(2)中心词是序数词、形容词最高级、the last/the only/the next 或被这些词修饰时，用不定式作定语。
Zhang Jian is the first Chinese to swim across the Bohai Sea.
He was the only one to finish the task on time.
(3)抽象名词 time, way, reason, chance, courage, opportunity, ability 等后以及不定代词 something, nothing, little 等后常用不定式作定语。
A subway is an effective way to solve traffic problems in a big city.
(4)“there be＋主语＋to do”和 have sth. to do 结构中，不定式也作后置定语。
There is nothing to worry about.
He has a lot of work to do today.
(1)作目的状语。可位于句首或句末，其前可加 in order/so as，但 so as to 不可位于句首。
I got up early (in order) to catch the 6：30 train.
I am glad to see you.
He smiled to think of a clever plan.
(3)作结果状语，表示出人意料或不太好的结果，常与 only 连用；而现在分词作结果状语则表示自然而然的结果。
I hurried to the post office, only to find it closed.
1．The old man sat in front of the television every evening, happy (watch) anything that happened to be on.
2．I dialed up corporate headquarters, only (tell) those names were not yet public.
3．Volunteering gives you a chance (change) lives, including your own.
4．The airport (complete) next year will help promote tourism in this area.
5．It's standard practice for a company like this one (employ) a security officer.
6． (free) ourselves from the physical and mental tensions, we each need deep thought and inner quietness.
7．They hurried to the station, only (find) their train had gone five minutes before.
8．He hurried to school only (find) nobody there.
9．She wanted (see) which shop offered the best service.
10．I feel it exciting (see) the movie Wolf Warriors Ⅱ which Wu Jing directed and starred in.