1.介詞的功能

介詞是一種虛詞，用來表示名詞或相當(dāng)于名詞的其它詞語句中其它詞的關(guān)系，不能單獨(dú)使用。介詞可與名詞或相當(dāng)于名詞的其它詞構(gòu)成介詞短語。介詞短語可在句中作定語，狀語，表語和賓語補(bǔ)足語。例如：

The boy over there is John’s brother. (定語)

The girl will be back in two hours. (狀語)

Our English teacher is from Australia. (表語)

Help yourself to some fish. (賓語補(bǔ)足語)

2.常用介詞的用法辨析

（1）表時間的介詞

1)at, in on

表示時間點(diǎn)用at。例如：at six o’clock, at noon, at midnight。表示在某個世紀(jì)，某年，某月，某個季節(jié)以及早晨，上午，下午，晚上時，用in。例如：in the ninettenth century, in 2002, in may, in winter, in the morning, in the afternoon等。表示具體的某一天和某一天的上午，下午，晚上時，用on。例如：on Monday, on July 1st, on Sunday morning等。

2)since, after

由since和after 引導(dǎo)的詞組都可表示從過去某一點(diǎn)開始的時段，但since詞組表示的時段一直延續(xù)到說話的時刻，因而往往要與現(xiàn)在完成時連用。而after詞組所表示的時段純系過去，因而要與一般過去時連用。例如：

I haven’t heard from him since last summer.

After five days the boy came back.

3)in, after

in與將來時態(tài)連用時，表示“過多長時間以后”的意思，后面跟表示一段時間的詞語。After與將來時態(tài)連用時，后面只能跟表示時間點(diǎn)的詞語。After與過去時態(tài)連用時，后面才能跟表示一段時間的詞語。例如：

He will be back in two months.

He will arrive after four o’clock.

He returned after a month.

（2）表示地點(diǎn)的介詞

1)at, in, on

at一般指小地方;in一般指大地方或某個范圍之內(nèi);on往往表示“在某個物體的表面”。例如：

He arrived in Shanghai yesterday.

They arrived at a small village before dark.

There is a big hole in the wall.

The teacher put up a picture on the wall.

2)over, above, on

over, on和above都可表示“在……上面”，但具體含義不同。Over表示位置高于某物，在某物的正上方，其反義詞是under。above也表示位置高于某物，但不一定在正上方，其反義詞是below。On指兩個物體表面接觸，一個在另一的上面。例如：

There is a bridge over the river.

We flew above the clouds.

They put some flowers on the teacher’s desk.

3)across, through

across和through均可表示“從這一邊到另一邊”，但用法不同。Across的含義與on有關(guān)，表示動作在某一物體的表面進(jìn)行。Throgh的含義與in有關(guān)，表示動作是在三維空間進(jìn)行。例如：

The dog ran across the grass.

The boy swam across the river.

They walked through the forest.

I pushed through the crowds.

4) in front of, in the front of

in front of 表示“在某人或某物的前面”，在某個范圍以外;in the front of 表示“在……的前部”，在某個范圍以內(nèi)。例如：

There are some tall trees in front of the building.

The teacher is sitting in the front of the classroom.

3.介詞的固定搭配

介詞往往同其他詞類形成了固定搭配關(guān)系。記住這種固定搭配關(guān)系，才能正確使用介詞。

(1)介詞與動詞的搭配

listen to , laugh at, get to, look for wait for, hear from, turn on, turn off, worry about, think of, look after, spend…on…， 等。

(2)介詞與名詞的搭配

on time, in time, by bus, on foot, with pleasure, on one’s way to, in trouble, at breakfast, at the end of, in the end等。

(3)介詞與形容詞的搭配

be late for, be afraid of, be good at, be interested in, be angry with, be full of, be sorry for等。

4.連詞的功能

用來連接詞，短語，從句或句子的詞叫連詞。連詞是一種虛詞，在句中不能單獨(dú)使用。連詞可分為兩類：并列連詞和從屬連詞。

5.并列連詞

并列連詞用來連接具有并列關(guān)系的詞，短語或句子。常見的并列連詞有：

(1)表并列關(guān)系的and, both…and, not only…but also, neither…nor等。

(2)表選擇關(guān)系的or, either…or等。

(3)表轉(zhuǎn)折關(guān)系的but, while等。

(4)表因果關(guān)系的for, so等。

6.從屬連詞

從屬連詞用來引導(dǎo)從句。常見的從屬連詞有：

(1)引導(dǎo)時間狀語從句的after, before, when, while, as, until, till, since, as soon as等。(2)引導(dǎo)條件狀語從句的if, unless等。

(3)引導(dǎo)原因狀語從句的because, as, since等。

(4)引導(dǎo)目的狀語從句的so that, in order that等。

(5)引導(dǎo)讓步狀語從句的though, although, even if等。

(6)引導(dǎo)結(jié)果狀語從句的so that, so…that, such…that等。

(7)引導(dǎo)比較狀語從句的than, as…as等。

(8)引導(dǎo)名詞從句的that, if , whether等。

7.常用連詞的用法辨析

(1)while, when, as

這三個連詞都可引導(dǎo)時間狀語從句，但用法有所不同。

1)當(dāng)某事正在進(jìn)行的時候，又發(fā)生了另一件事。While, when, as 都可用來引導(dǎo)表示“背景”的時間狀語從句。例如：

As/When/While I was walking down the street I noticed a police car.

2)當(dāng)兩個長動作同時進(jìn)行的時候，最常用的是while。例如：

While mother was cooking lunch, I was doing my homework.

3)當(dāng)兩個動作都表示發(fā)展變化的情況時，最常用的是as。例如：

As children get older, they become more and more interested in things around them.

4)當(dāng)兩個短動作同時發(fā)生時，或表示“一邊…一邊…”時，最常用as。例如：

Just as he caught the fly, he gave a loud cry.

She looked behind from time to time as she went

5)當(dāng)從句的動作先于主句的動作時，通常用when。例如：

When he finished his work, he took a short rest.

6)當(dāng)從句是瞬間動作，主句是延續(xù)性動作時，通常用when。例如：

When John arrived I was cooking lunch.

（2）as, because, since , for

這四個詞都可表原因，但用法有區(qū)別。

1)如果原因構(gòu)成句子的最主要部分，一般用because。因此，because引導(dǎo)的從句往往放在句末。例如：

I stayed at home because it rained.

---Why aren’t you going?

---Because I don’t want to.

2)如果原因已被人們所知，或不如句子的其它部分重要，就用as或since。Since比as稍微正式一點(diǎn)。As和since 引導(dǎo)的從句一般放在句子的開頭。例如：

As he wasn’t ready, we left without him.

Since I have no money, I can’t buy any food.

3)for用來補(bǔ)充說明一種理由，因此，for引導(dǎo)的從句幾乎可以放在括號里。For引導(dǎo)的句子不放在句子的開頭。例如：

I decided to stop and have lunch----for I was feeling quite hungry.www.zhongkao5.com//

（3）if, whether

if和whether都可作“是否”講，在引導(dǎo)賓與從句是一般可互換。例如：

I wonder whether (if) you still study in that school.

I don’t know whether (if) he likes that film.

在下列情況下，只能用whether,不能用if：

1)引導(dǎo)主語從句時。例如：

Whether he will come to the party is unknown.

2)引導(dǎo)表語從句時。例如：

The question is whether I can pass the exam.

3)在不定式前。例如：

I haven’t made up my mind whether to go there or not.

（4）so…that, such…that

1)so…that中的so是個副詞，其后只能跟形容詞或副詞，而such…that中的such是個形容詞，后接名詞或名詞短語。例如：

I’m so tired that I can’t walk any farther.

It was such a warm day that he went swimming.

2)如果在名詞之前有many, much, little, few時，用so,不用such。例如：

He has so little education that he is unable to get a job.

I have had so many falls that I am black and blue all over.

（5）either…or…， neither…nor, not only…but also…

這三個連詞詞組都可連接兩個并列成分。當(dāng)它們連接兩個并列主語時，

謂語動詞要隨相鄰的主語變化。例如：

Either you or he is wrong.

Neither he nor his children like fish.

Not only the teacher but also the students want to buy the book.

（6）although, but

這兩個連詞不能用在同一個句子中。例如：我們不能說“Although he is

over sixty, but he works as hard as others.”這個句子應(yīng)改為：Although he is over sixty, he works as hard as others.或He is over sixty, but he works as hard as others.

（7）because, so

這兩個連詞同樣不能用在同一個句子中。例如：我們不能說“Because John

was ill, so I took him to the doctor.” 這個句子應(yīng)改為Because John was ill, I took him to the doctor.或John was ill, so I took him to the doctor.

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