to什么时候作介词?

TO做介词的用法：
1.(表示方向、目的地) 向
She went to the window and looked out.她走到窗前向外望去.
2.去 (参加)
He came to dinner.他来吃晚饭.
3.附着
There was a piece of cloth tied to the dog's collar.有一条布系在狗项圈上.
4.(表示方位) 在
Hemingway's studio is to the right.海明威的工作室在右边.
5.给 [用法v+n+to+n]
He picked up the knife and gave it to me.他捡起刀并拿给我.
6.(表示行为或情感针对的目标) 对于 [用法：adj/n+to+n]
Marcus has been really mean to me today.马库斯今天确实一直对我不友好.
7.对 (表示受某事影响) [用法：adj/n+to+n]
He is a witty man,and an inspiration to all of us.他是一个风趣的男人,对我们所有的人是一种鼓舞.
8.对… (说)
I will explain to them that I can't pay them.我会向他们解释说我无法付钱给他们.
9.(表示反应或情感) 致使
To his surprise,the bedroom door was locked.使他吃惊的是,卧室的门是锁着的.
10.在…看来
It was clear to me that he respected his boss.在我看来,显然他尊重他的老板.
11.(表示状态或形势等的变化) 成为
The shouts changed to laughter.叫喊声变成了笑声.
to还有不做介词的情况,比较少：
CONVENTION（习惯表达）：……（程度副词之类的） to
If you say "There's nothing to it," "There's not much to it," or "That's all there is to it," you are emphasizing how simple you think something is.(表示强调) 容易得很 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。。。。
如：I get used to getting up early我习惯早起，这里的to便是介词另外，你是想从哪个角度去理解呢？我觉得你只知道大概就行了，要是从英语专业角度给你具体分析吧，那可以有好多呢那就简单了，常见的一些你记住就可以了look forward to doing

say no to doing

pay attention to doing

prefer doing to doing

get used to doingcontribute to doing
devote to doing

commit to doing不客气！感叹句那个你看懂了没有？哦，好的