介词短语在句中的作用
介词不能单独在句子当中担当成分，它后面必须接名词、代词或相当于名词的其他词类搭配(介词+宾语)构成介词短语;和动词搭配构成短语动词，然后才能够在句子当中充当成分。 一、介词的搭配与选择
介词不能在句子中独立充当一个成分，而需要与其后面的宾语相结合，成为介词短语，在句中充当一个成分。所以选用什么介词要根据其后面所接的宾语而定。但是，有时介词也受其前面用词的限制，因此，许多情况下也应根据介词前面的词选用相应的介词。
二、介词的语法功能
介词与其他词类或成分结合后方能在句子中充当语法成分，构成介词短语。介词短语可以作定语(须后置)、状语、表语、宾语补足语、另一个介词的宾语，间或作主语等。
例如：
The skyscraper in the distance isa five-star hotel.(定语)
Her eyes were tired from long reading.(状语)
The decision is of great importance to me.(表语)
They found the machine in a bad state.(宾语补足语)
A pretty girl appeared from behind the curtain.(介词宾语)
On purpose or not on purpose is of great difference.(主语)
三、介词的分类
介词是用于名词词组或相当于名词词组的结构之前，表示词语之间意义关系的词类。 英语常用的介词大致可分为四类：
1.简单介词
顾名思义，简单介词是指由一个单词构成的介词，也是使用最频繁的一类介词。简单介词也可能由形容词、副词、分词、名词、连词等转变而来。常用的简单介词有：
at，about，above，across，after，among， against，before，behind，below，beside，between，beyond，but，despite，during，except，for，in，of，on，over，near，past， round，since，through，till，until，with，up等。
2.合成介词
指由介词+其它介词或副词构成的介词。常用的合成介词有：
inside，into，onto， outside，throughout，towards，within，without等。
3.二重介词
指由两个单一的介词并列在一起，作为一个介词使用并表达一个完整意思的介词。常见的二重介词有：
from among，from behind，from under，until /till after等。介词短语在句中的作用
4.短语介词
指由介词+介词、介词+名词、介词+分词、介词+动词、介词+形容词、介词+副词等构成的短语.常用的有：
according to， along with，in front of，by means of，in spite of，together with，with regard to等。短语介词与介词短语不同。介词短语是由介词加宾语构成，本身可作句子成分，如定语或状语等，可单独使用;而短语介词是用作介词的短语，不可独立使用，本身不能作句子成分，后面要跟名词、动名词或代词等。
四、介词的宾语
介词的宾语可以是名词、代词或其他词类或句子等。例如：
名词：The car ran into a wall，and two men were killed.
代词：Wherever he went，he carried the photo with him.
形容词：Your plan is far from perfect.
副词：I can't see the tower clearly from here.She came from afar.
动名词：He entered the room without taking off his hat.
不定式：He did nothing but cry.
介词短语：She often studies till after midnight.
数词：In nine out often he won't come.
疑问词+不定式：The problem of how to get enough money is difficult to settle.
疑问词引导从句：He does not care about who will be promoted.
that引导的从句：Man differs from other animals in that man can laugh and speak.
五、介词短语的句法功能
1.作定语
The key to the door is missing.
2.作表语
As we know, Japanis to the east of China.
3.作状语
1) On Sundays, the family are mostly out. (时间状语)
2) On top of the hill stands a TV tower. (地点状语)
3)All the work must be done by hand. (方式状语)
六、介词的复合结构
1. 介词+宾语+形容词
He is used to sleeping with all the windows open.
2. 介词+宾语+分词
The wounded boy glared at the nobleman with his teeth clenched.
3. 介词+宾语+不定式
The cat humped its back just like a fierce tiger to jump upon me.
4. 介词+宾语+副词
The little boy rushed out of the house without anything on.
5. 介词+宾语+介词短语
The teacher entered the classroom with a book under his arm.
七、介词的叠用
在少数介词之后还可接另一个介词短语，也就是我们所称的二重介词。如：
The naughty boy suddenly rushed out from behind the tree to frighten the girl.
介词+and+介词
Not knowing what to do, the worried officer walked up and down the room.
There are many trees in and outside the town.
八、介词的固定搭配
在英语中固定搭配的介词词组和短语介词很多，平时需要加强记忆。此处讲解几个常见的动词与介词的固定搭配，并且就较容易混淆的介词搭配进行比较、分辨。
1.act as 担任 act for 代理
2.apply to 应用于，适合于，向……申请 apply for 申请，要求
3.belong to 属于 belong in住在，应该…… belong with 应归于(类别，范畴等)
4.call on 号召，请求，拜访 call at 探访(at后接地方) call in 请医生，召集，收集 call to 高声唤(某人)
5.compare with 跟……相比较 compare to 把……比作，与……相比
6.correspond with 与……通信;适合 correspond to 相当于
7.deal in 做生意，经营(=engage in) deal with 对付，论及，与……交往(=cope with)
8.play with 玩(某物) play at玩(某种游戏) play on 玩(某种乐器)
9.suffer from 患(病)，受……祸患.
10.wait on 伺候 wait for等待
九、常易混用介词的区别
1. 表示“上、下”等方位的介词。
2. 表示地点的in和at的区别
a) at表示位置，in表示“在…内”如：
— Where is he? — He is at the cinema. (问话者想知道的是位置)
— Is he in the cinema? — Yes, he is. (问话者可能已经在影院门外)
b) at表示小地点，in表示大地点
They arrived at the village at seven.
They arrived in Beijing at seven.
3. in, to和on在方位名词前的区别
in表示在某范围之内;to表示某范围之外的地方;on表示“毗邻、接壤”
Taiwanlies in the east ofChina.
Taiwanlies to the east of the mainland ofChina.
Mongolia (蒙古) is (lies) on the north of China.
4. 表示时间的in和after
用于将来时态时，in后面接“时段”;after后面接“时点”。试比较：
He will be back in five hours.
He will be back after five o'clock.
after后面也可接“时段”，但应该用在过去时态的句子中。
They came back after five days.
十、常见考法
一些常见介词如in, at, for, to, by, on, against, between, along, below, with, as等的辨析;
一些介词短语如next to, far from, out of, due to, in all, in fact, in short, in return, in search of, in place of, for lack of, for fear of, by nature, in case, by chance 的辨析.
十一、误区提醒
1. 一些介词的基本用法不清;2. 一些多义介词的用法弄混;3. 一些介词短语不会灵活运用。
【典型例题】
1.Would you mind not picking the flowers in the garden? They are ____ everyone's enjoyment.
A.in B. at C. for D. to
解析: 错选D。for everyone's enjoyment 意为“为了大家欣赏”，for在此处为一基本用法，但受to one's joy的影响错选答案。正确答案为C。
2. So far, we have done a lot to build a low-carbon economy, but it is ____ ideal. We have to work still harder.
A. next to B. far from C. out of D. due to
解析：错选C。next to 挨着，far from 远非，out of 出于，due to 因为，根据意思，有空的句子要表达“但还很不理想”。正确答案为B。