介词
是一种虚词，不能单独做句子成分，必须和名词或代词（或相当于名词的其他词类，短语或句子）构成介词短语，才能在句子中充当一个成分。
Ⅰ. 分类及作用 1. 分类
1） 简单介词：如 at, in, on, besides, since, of 等 2） 合成介词：如inside, out of , onto, without等
3） 介词短语：如because of, next to, instead of, due to 等 4） 二重介词：如from behind, until after 等
5） 分词介词：如concerning/regarding/respecting(关于)，considering，following， given，
including，owing to，saving等。 2. 介词在句中的作用 1） 作定语
A friend in need is a friend indeed. The house opposite ours are being pulled down. 2） 作状语
With production up by 60%, the company has had another excellent year. 3） 作表语
Japan is to the east of China. 4） 作宾补
Make yourself at home. We found her in better spirits. 3. 介词后接形容词通常加上being。
He was dismissed from his job for being absent-minded while working. 现代英语中，某些介词后可省略being直接接形容词。这种用法仅限于某些含介词的短语，通常比较固定，不能随意套用: 1) take …for granted
I took it for granted that you would stay with us. 2) far from
His explanation was far from satisfactory 3) anything but
He is anything but angry 4) kind of
He looks kind of pale after his illness. 5) sort of
She is sort of excited 6) consider… as
We consider the wire as disconnected 7) accept…. As
We accept the conclusion as true. 8) regard….as
Do you regard it as necessary I should come？ Notes：regard…as 后还可以接介词短语和分词
He regarded the account of the accident as of very little value. They regarded the contract as having been broken After a few rounds of talks, both sides regarded the problem as settled. 4. 省略介词直接接名词的情况
当“of + age/color/height/length/size/shape/volume”等作表语时，通常可省略of，直接接名词 They were (of) the same age. He was (of) medium height. 5. It is of /for sb. to do sth.
Ⅱ. 几个常用介词用法 用法 表时间 表示在附近 表地点 表示除外 表方位 表示“经由，通过，穿过” 表示“在…上/下” 表方式 表原因 表价格，比率，对比 表属性，特性 表比较 常用介词 At, in, on, by, for, through Near, by, beside, at At, in, on Besides, except, except for, but, but for In, to, on Across, by, through Above, below, over, under, on, beneath By, through, with Through, with, from, for, at, owing to, due to, because of, on account of , thanks to At, by, for, against Of, with As, like 1. 表时间
At, in, on, by, for, through 的区别： At 1) 指时间的一点，时刻等
They come home at sunrise (at noon, at midnight, at ten o?clock, at day break, at dawn) 2) 较短暂的一段时间，可指某个节日或被认为是一年中标志大事的日子。
He went home at Christmas ( at New Year, at the Spring Festival, at night, at midsummer). At the beginning (middle, end) of that month he was sick. His grandfather died at seventy two. In 1) 在某个较长的时间（如世纪， 朝代，年，月，季节，以及泛指的上午，下午和傍晚等）内。 He was born in 1942. He did it in the holidays. 2) 在一段时间之后。
▲一般情况下，用于将来时间时，谓语动词为“一时性的动作” in作“在…以后” He will arrive in two hours.
▲ 谓语动词为延续性动作时，in作“在….以内”解 These products will be produced in a month.
▲after 用于将来时间也指 一段时间之后，但其后是时间点（如： after two o?clock），
而不是时间段
On 1) 具体的时日或特定的时间， 如某日，某节日，星期几等。
On May 4th (on Sunday, on New Year?s day, on Christmas Day), there will be a celebration.
He will come to meet us on our arrival. 2) 在某个特定的早晨，下午或晚上
He died on the eve of victory.
He arrived at 10 o?clock on the night of the 5th. 3) 准时，按时
If the train should be on time, I should reach home before dark. By 1) 不迟于，在（某时）前 He must have returned by now.
Jack had made some friends by the time you came. He will come by six o?clock.
By then he was more than fifty years of age. 2) 在….间， 在…..时候
He worked by day and slept by night. I don?t like traveling by night.
For 1) (年， 月，日，时等)….之久 He was absent from school for a week. I have been here for three days. 2) 指定的时刻。
The operation was fixed for Friday.
The ceremony was arranged for two o?clock/March 1st.
The meeting was planned for 10 o?clock, but now it has to be moved to a later time. Through 同throughout
He guarded us all through the night.
2. 表示在附近
near 表示相对的近，实际距离可能还很远 Suzhou is near Shanghai。
There is a post office near our school. By, beside 都表示‘靠近’，实际距离不可能很远，但beside比by 更具体地表示出“在…旁边”
He was sitting beside her.
There is a big tree by the river.
At 也有在旁边的意思，但多表示有目的的行为所处的位置，而by和beside仅表示位置关系
The students are sitting at the desks listening to the teacher.
Several students are sitting by/ beside the window talking about a film.
3. 表地点
At 1）用于指较小的地方。 I shall wait for at the station. 2) 用于门牌号前
He lives at 115 Fuzhou Road.
In 1) 用于较大的地方。 He lives in Shanghai.
2) 商店，机关，学校等，若看作一个地点（point）用at， 若看作一个场所（place）用in
I met him at the post office. I am working in the post office.
On 表地点，一般指与面或线接触
1) 在…..之上
The picture was hanging on the wall.
He put the book on the table and sat on the chair. 2) 在…. 旁边
He lives in a house on the river. New York is on the Hudson River. 但：he sails on the river every day. 3) 在….里
He lives on Fifth Avenue.
He has few friends on the campus. 4. 表示除外 Besides
Besides, Mr. Wang, we also went to see the film. Notes: besides 用于否定句，与except， but 同义 We have no other books besides (except) these.
Except
1) We all went to see the film except Mr.Wang.
2) 后可接名词性从句，状语从句，副词，介词短语或不定式。 I know nothing about that fellow except that he lives across the street. My mother usually goes to work by bike except when it rains. We looked everywhere except there.
I looked everywhere except in the bedroom.
接不定式，带to 不带to 取决于except前是否含有do Mary does everything except wash the car. It has no effect except to make him angry. Except 用在句首，往往加for
Except for this, everything is in order. =everything is in order except this.
Except for 有除了…之外， 被排除的部分不属于同类的人或物，而是部分修正句子的意思
The composition is very good except for a few spelling mistakes.
Note: except for 还有“要不是（因为）…” 的含义，相当于‘if it were not for’ She would leave her husband except for the children.
But 意为“除了”, 与except 同义，except强调被排除的部分，but则强调整句的内容， 常修饰否定意义的代词或疑问代词
Nobody knew it but me.
Who would do such a thing but Jack? But for
But for the rain, we would have a pleasant jouney. 5. 表方位
Guangdong lies in the south of China.
Fujian lies to the south of Jiangsu Province Mongolia lies on the north of China. 6. 表 经由，通过，穿过
Across 作“穿过，跨过”解，指横过一个平面或横过一条直线，或静止的的对面的位置，相当于 “ from one side to the other of , on the opposite side of ” A bird flew across the sky.
Kate went across the street to make some purchases.
By 作“经由，取道， 通过”，表移动的方向。 He rose quickly and went out by another door. I shall return possibly by Nanjing.
Through 作“从…通过， 穿过（从这一端到另一端）”， 指通过一个三维或被看作三维的空间。
The sunlight was coming in through the window. She led the soldiers through the forest. 7. 表 “在….上/下”
Above, below, over , under, on, beneath.
Below 除表示方位外，还可用于指位置， 职位， 程度，价值， 品德，或年龄低于所提及的人或物。
His position in the firm was below his brother?s. The cost of the work was below twenty dollars.
Over ?在….之上? （表示垂直之上或表示附于某物之上并将之遮住）
8. By, through, with 表示方式，方法，手段的区别。 By 表示方式，方法，手段的用法 1） 表示以一般的方法或方式 We often met by appointment.
The bicycle is made by machine, not by hand. The streets are lighted by electricity.
No one in those days could live by writing poems. The freight was charged by weight.
Notes: 表示以某种方式行事， 名词前不加定冠词。 By weight, by auction, by volume, by contract. 2) 表示传达，传递的方式或媒介：
How did you send the letter, by airmail or by email? By letter, by radio
4) 表示用交通工具，通讯工具， 后接名词单数，不加冠词。 He came by train but his wife came by bus. They came by air and left by ship.