英语中单个动词（以v.表示）只能充当谓语，那么如果想让v.充当主语、宾语、表语、同位语、状语、补语、独立成分等，则需要改变v.的形式。具体方法有四种：不定时to do形式(to v.)、现在分词（v.+ing）、动名词（v.+ing）和过去分词（v.+ed），这就是非谓语动词结构。
基本结构：to do/ doing / done
To be or not to be（名词当主语） - that is the question.
Seeing(动名词，主语) is believing（动名词，表语）.
He came running（现在分词作状语） into the room.
The prisoner came in, followed（过去分词，状语） by a guard.
- 非谓语作定语时通常置于名词之后（后置定语），即：n+ to do/ doing / done;
- 非谓语作状语时通常的形式是：to do/ doing/ done + 句子，或：句子 + to do/ doing/ done。
- 非谓语to do 表将来。
When Mrs. Richards walded towards him(时间状语从句), he fled, slamming（非谓语） the door behind him（doing 短语作便随状语）.
To understand(不定式当主语) the situation completely requires more thought than we expected.
To understand the situation completely （主语）。
It(形式主语) is almost impossible to take your mind off the journey.
to take your mind off the journey.充当主语。
The baby pulls the tablecloth off the table, smashing（摔） half your best crockery and cutting himself in the process.(现在分词作伴随状语)
Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily(便利地) available, should know about the various possible methods for making water safe(定语).
planning a trip to remote areas(后置定语修饰主语those).
intending to live in countries(后置定语修饰主语those).
Mr.Green stood up in defense of the 16-year-old boy, saying that he was not the one to blame(必须使用主动，主动表被动).
It(形式主语) remains to be seen whether Jim will be fit enough to paly in the finals.
When comparing different cultures, we often pay attention only to the differences without noticing.
Faced with so much trouble, we failed to complete the task on time.
Facing so much trouble, we failed to complete the task on time.
Faced with = facing 面对（🌟）
Peter received a letter just now saying his grandma would come to see him soon.(❤️)
As the light turned green, I stood for a moment, not moving, and asked myself what I was going to do.
Come on, please give me some ideas about the project. Sorry. With so much work filling my mind, I almost break down.
Jenny hopes that Mr.Smith will suggest a good way to have her written English improved in a short period.
The children went home from the grammar school, their lessons finshed for the day.
– The last one to arrive one pays the meal. – Agreed!
The message is very important, so it is supposed to be sent as soon as possible.
– They are quiet, aren’t they? –Yes. They are accustomed to(习惯于) not talking at meals.
It is one of the funniest things found on the Internet so far this year.
We finished the run in less than half the time allowed.
The trees blown down in the storm have been moved off the road.
分类：to do, doing, done.