to 有两个功能，首先 to 可以作为所谓的infinite marker，也就是标记后面的动词为非限定性动词。在 want to 和 begin to 中，to 扮演的就是这个角色。
to 的另外一个功能就是作介词，就如同 for 或者 of 这样的介词 一样。而我们知道 for 或者 of 后面是加 doing的，因此这就解释了为什么当 to 作介词时后面也应该是 doing。
如果 to 后面可以接一个名词 (更准确的讲法是名词短语)，那么 to 这时就是介词，如果 to 后面不能接名词，那么这个 to 就是infinite marker。
有一部分单词是既能跟动名词，也能跟动词不定式，比如 ：
be used to doing sth 被用来做某事 如A pen is used writing
be used to do sth 被用来去做某事如The pen is used to kill the bird
扩展资料：
1、下列结构用带to的动词不定式和ing形式含义相同：
begin to do/doing
start to do/doing
continue to do/doing
2、既用不带to的动词不定式又用现在分词的句型： 用不带to的动词不定式强调动作的完成过程；用现在分词强调动作的进行状态。
hear sb do sth./doing
listen sb do sth./doing
look at sb do sth./doing
see sb do sth./doing
watch sb do sth./doing
notice sb do sth./doing
两种情况下的to的词性是不一样。当to后面接do原形的时候，是当作不定式来用，当后面接doing的时候，它是当作介词，一般to后面接的都是do原形，只有在少数的固定词组，后者特殊用法中才当作介词接doing，比如get used to习惯于……
①to do sth
Eg：The students wanted to watch these recordings over and over.
②doing sth
Eg：I look forward to meeting the digitized representation of Joel.
扩展资料：
to的用法：
向；至；往：
She's going to London.她要去伦敦。
Turn to the left.向左转。
Pisa is to the west of Florence. 比萨在佛罗伦萨的西面。
He has gone to school.他上学去了。
2.（用于表示一系列事物或一段时间的尽头或限度） 直到：
from Monday to Friday从星期一到星期五
from beginning to end 从开始到结束。
3.用于表示接受者：
Give that to me.把那个给我。
I am very grateful to my parents.我很感激我的父母。
What have you done to your hair?你把头发怎么搞的？
Sorry I didn't realize you were talking to me.对不起，我不知道你是在跟我说话。
4接触到；针对：
He put his hands to his ears.他将两手捂住耳朵。
They sat back to back.他们背对背坐着。
She made no reference to her personal problems.他没有提及自己的个人问题。
5.达到某种状态：
The meat was cooked to perfection.这肉煮得恰到好处。
His speech reduced her to tears(=make her cry).他的话令她流泪。
6.（用于引出比较中的另一部分）：
I prefer theatre to opera.我喜欢戏剧，甚于歌剧。
7.（用于表示数量）每```等于：
How many dollars are there to the euro?多少美元等于一欧元？
8.（用于表示时间）在```之前：
It's ten to three.(=ten minutes before three o'clock).现在是三点差十分。
参考资料来源：百度百科-to（英语词语）
本回答被网友采纳一：表示相对，针对
be strange (common, new, familiar, peculiar, distinct, sensitive, immune, vulnerable, indispensable) to
Air is indispensable to life.
Aircrafts are vulnerable to interference caused by radiation.
This injection will make you immune to infection
二：表示对比，比较
1：以-ior结尾的形容词，后接介词to表示比较，如：superior ,inferior,prior,senior,junior
The quarrel happened prior to my arrival.
2:一些本身就含有比较或比拟意思的形容词，如equal，similar，equivalent，analogous
A is similar to B in many ways.
3：表示一些先后顺序的形容词，如：second,subsequent,next,preliminary,preparatory
Subsequent to the war,they returned to their hometown.
4:to也偶尔出现在个别动词之后,与动词形成固定词组,表示比较,如:prefer to,compare to,in contrast to compare to sth.表示比喻或比拟,而compare with sth.表示比较,如:
World is usually compared to a stage
Compared with his past,he has changed a lot.
Prefer的正确句型是:prefer A to B或prefer doing A to doing B,但当prefer后接动词不定式时,表示比较的介词to就要改成rather than ,如:
The undaunted soldier preferred death to surrender.
Many people prefer spending money to earning money.
They prefer to pursue careers rather than remain home as house wives.
5:to与及个别的名词构成比较之意,如:alternative
Going to an under water concert is a great alternative to going to dinner.
三:表示修饰关系
1:表示回复,反应意思的词,如:answer to question,
solution to problem,response to inquiry,reaction to proposal,reply to letter
2:表示建筑构件的词汇,如: entry,entrance,approach,access,passage,exit,vent,path
the approach to a bridge引桥
the approach to science
Half of the population was estimated to have no access to the health service.
The access to education 接受教育的机会
The access to medical care 享受公费医疗的权利
4:表示人物职位和官衔的词,如:assistant to manager, ambassador to Spain, successor to tradition, heir to throne,deputy to the National People’s Congress
advisor to the Prime Minister
5:表示权利和许可的词汇,如:right,admission
The employee finally got the admission to the boardroom.
Everyone has an equal right to ……..
6:表示栅栏或障碍的词汇,如:bars to development,the barrier to progress
7:表示与书籍,文本相关的词,如:introduction to passage.
8:表示恭喜或是祝贺,如:
The director proposed a toast to the health of the guests.
Let’s drink to Dick’s success in business
9:另外还有一些名词符合这种用法,有的具有两者息息相关,缺一不可的含义.如:key to door,invitation to party,
guide to action,limitation to life,accessory to school
四:to还具有依据,伴随,和着节奏的含义,如:sing to piano, chance to the tune, stamp to the rhythm of the song, add salt to taste
五:表示趋势或倾向,如:tend to,be prone to,be inclined to,be apt to,be liable to
He’s liable to seasickness.
You are liable to come to wrong conclusion.
六:表示对事情的坚持与执着,如:sick to,hold o,adhere to,cling to
He still holds on to his original views.
七:表示约束,局限,如:limit to,confine to,resrict to
He’s confined to the house by illness.
He confined his remarks to scientific mangement.
八:表示一种习惯或是一种适应性,如:get (be) to,used to,be accustomed to
Finally,the students got used to my teaching method.
十:表示起因和原由,如wing to,due to,thanks to,attribute to,come down to
The flight was cancelled due to the thick fog.
The famous artist attributed his success to his wife.
十一:表示目的或结果,如:aim to,lead to,give rise to
I aim to be an excellent college teacher.
His conceit lead to his failure.
These bad condition has given rise to a lot of crises
十二:表示命运,注定,如:be doomed to,be destined to,
All military adventures by the two super powers are doomed to fail.
十三:表示数量上的积累或增加,如:in addition to,add to,amount to
In addition to relief supplies,he also presented with some money.
The annual output of steel amounts to 1200 tons.
十四:表示全身心投入的含义,如:be addicted to,contribute to,devote to,commit to
He is determined to devote all his life to his.
十五:表示展望或是回顾,如:look forward to反date back to
The church dates back to the 13th century.
十六:表示方位概念.如:close to,next to
I don’t like wool next to my ski
十七:表示依靠或借助,如:resort to,turn to,appeal to,
He usually appeals to arms to settle the territory dispute.
十八:表示有关注,关于:as to,with regard to
十九:表示关注或重视,如:pay attention to,attach to,
We should attach primary importance to job training.
二十:表示依据或是根据,如:according to,in proportion to
According to today’s newspaper,the match will be postponed.
The lending countries subscribe towards capital stock in proportion to their economic importance.
二十一:表示应该或必须含义的句式,如:
It’s time to get up.
We are supposed to get here at seven.
It’s up to this country to ban nuclear weapons.
二十二：表示相关联，相连接，如：be related to,be relative to,in relation to,be relevant to,link to
Investigate all the facts related to the problem.
People often linked walth to happiness.
二十三：表示反对和赞同。
1：to引导的表示反对，抗拒，对抗意义的词组。Be opposed to,be oppsist to,be contrary to,be adverse to,be resistant to,be contradictory to,object to,oppose to,deny tp,be aline to
These buildings are resistant to earthquake.
They are to tally opposed to any changes being made in the plans.
2:to引导的表示同意，赞同意义的词组：consent to,subseribe to,
The employer consented to give him a salary raise.表示调整，使符合，使适应的含义，如：adapt to,commodate to,adjust to,conform to,habituate to,fit to,suit to,correspond to,cater to
She tried to habituate herself to the style of plain living.
Your action should conform to the interests of the people.
They offered various foods to cater to the need of customers.
His words doesn’t fit to his actions.
Suit your writing style to the masses.
3:表示投降,屈服,服从的含义,如:be subject to,be subordinate to,submit to,subject to,surrender to,give in to,confess to,admit to.
The minority is subordinate to the majority少数服从多数
Countries nearby oceans are always subject to earthquake.
He confessed to having robbed the woman of her wallet.
We’re not the kind of people to yield to any military threat.
常用词组
respond to（反应）,appeal to（吸引）,catch on to（理解）,listen to（收听）,used to（过去常常）,give birth to,attend to（照料）,see to（负责）,be entitled to（有权）,belong to（属于）,come to（苏醒）,stand up to（勇敢面对）,help oneself to（请自便）,refer to,to the point（切题）,
Train them to stand up to any severe test in hard.
The ticket entitled you to a free meal in the luxury hotel.
See to it that the children get a hot meal after their swim.
You will catch on to the job shortly after wards.
People usually refer to television for up-to-the-minute news有什么不懂就问吧