連詞比較
I and 與or
1) 并列結(jié)構(gòu)中，or通常用于否定句，and用于肯定句。
2) 但有時(shí)and 也可用于否定句。請(qǐng)注意其不同特點(diǎn)：
There is no air or water in the moon.
There is no air and no water on the moon.
在否定中并列結(jié)構(gòu)用or 連接，但含有兩個(gè)否定詞的句子實(shí)際被看作是肯定結(jié)構(gòu)，因此要用and。
典型例題
---I don't like chicken ___ fish.
---I don't like chicken, ___ I like fish very much.
A. and; and B. and; but C. or; but D. or;and
答案C。否定句中表并列用or, but 表轉(zhuǎn)折。
判斷改錯(cuò)：
(錯(cuò)) We will die without air and water.
(錯(cuò)) We can't live without air or water.
(對(duì)) We will die without air or water.
(對(duì)) We can't live without air and water.
3 )表示選擇的并列結(jié)構(gòu)
(1) or 意思為"否則"。
(2) either…or 意思為"或者……或者……"。注意謂語動(dòng)詞采用就近原則。
Either you or I am right.
判斷改錯(cuò)：
(錯(cuò)) They sat down and talk about something.
(錯(cuò)) They started to dance and sang.
(錯(cuò)) I saw two men sitting behind and whisper there.
(對(duì)) They sat down and talked about something.
(對(duì)) They started to dance and sing.
(對(duì))I saw two men sitting behind and whispering there.
解析：
第一句： and 連接兩個(gè)并列的謂語，所以 talk 應(yīng)改為 talked。
第二句：and 連接兩個(gè)并列的動(dòng)詞不定式，第二個(gè)不定式往往省略to，因此sang 應(yīng)改為 sing。
第三句：and 連接感觀動(dòng)詞saw 后面的用作的賓補(bǔ)的兩個(gè)并列分詞結(jié)構(gòu)，因此whisper應(yīng)改為whispering。
注意：and 還可以和祈使句或名詞詞組連用表示條件。(or也有此用法)
Make up your mind, and you'll get the chance.
= If you make up your mind, you'll get the chance.
One more effort, and you'll succeed.
= If you make one more effort, you'll succeed.
II but表示轉(zhuǎn)折，while表示對(duì)比。
Some people love cats, while others hate them.
典型例題
--- Would you like to come to dinner tonight?
--- I'd like to, ___ I'm too busy.
A. and B. so C. as D. but
答案D。but與前面形成轉(zhuǎn)折，符合語意。而表并列的and，結(jié)果的so，原因的as都不符合句意。
III so, therefore
He hurt his leg, so he couldn't play in the game.
注意：
a. 兩個(gè)并列連詞不能連用，但therefore, then, yet.可以和并列連詞連用。
You can watch TV, and or you can go to bed.
He hurt his leg, and so / and therefore he couldn't play in the game.
b. although… yet…，但although不與 but連用。
(錯(cuò)) Although he was weak, but he tried his best to do the work..
(對(duì)) Although he was weak, yet he tried his best to do the work.
IV 比較so和 such
其規(guī)律由so與such的不同詞性決定。such 是形容詞，修飾名詞或名詞詞組，so是副詞，只能修飾形容詞或副詞。so 還可與表示數(shù)量的形容詞many，few，much， little連用，形成固定搭配。
so + adj. such + a(n) + n.
so + adj. + a(n) + n. such + n. (pl.)
so + adj. + n. (pl.) such +n. (pl.)
so + adj. + n. [不可數(shù)] such +n. [不可數(shù)]
so foolish such a fool
so nice a flower such a nice flower
so many/ few flowers such nice flowers
so much/little money. such rapid progress
so many people such a lot of people
so many 已成固定搭配，a lot of 雖相當(dāng)于 many，但 a lot of 為名詞性的，只能用such搭配。
so…that與such…that之間的轉(zhuǎn)換既為 so與such之間的轉(zhuǎn)換。
Eg :The MP3 cost me ________ money that I ccouldn't afford to buy it .
A .so much .B .such much C .so many D . such many .(Key :A )
注意:too .... to .. ,so ..... that .... , such .... that .... , enough ..... to ...., 的互換.
so that to = in order to /that 的用法.
Eg A .He is too young to go to school.
B .He is ____ a young boy _____ he ____ go to school .
C .He is ____ young ____ he ____ go to school .
D .He isn't ______ _______ ______ go to school (Keys :B :such , that , can't C :so ,that ,can't .D : old ,enough to )
易錯(cuò)分析：
①關(guān)于not…until
He stayed there until it was very late.
句中，stay是可延續(xù)性動(dòng)詞，所以不用not。
He didn't leave until it was very late.
句中，leave是不可延續(xù)性動(dòng)詞，所以用not
②because, so;although, but
上面已經(jīng)提到，because和so及although和but不連用。
例如:
Because he was late, he didn't catch the first bus.
一定不可以說
Because he was late, so he didn't catch the first bus.
③or還是and
祈使句+or+陳述句前后是對(duì)立的
祈使句+and+陳述句前后是統(tǒng)一的
(or或and后的陳述句，常用一般將來時(shí))
Study hard, or you won't pass the exam.
Study hard, and you will pass the exam.
兩句都可以轉(zhuǎn)換成“If條件句+主句”形式，注意：要去掉or和and：
If you don't study hard, you won't pass the exam.
If you study hard, you will pass the exam.
④because, since, as, for表示原因時(shí)的區(qū)別
盡管because, for, since, as都表示原因，但是用法上有不同.
because通常表示說話人認(rèn)為這種理由或者原因是聽話人所不知道的.
如:
He didn't attend the meeting because he had too much work to do.
since表示的原因是人們已知的事實(shí)，常譯作“既然”。
如：
Since he can't answer this question, you'd better ask someone else.
as表示原因與since差別不大，只是語氣更弱,多譯為“由于”
如：
As I haven't seen the film, I can't tell you what I think of it.
for表示因果關(guān)系時(shí)，只能放在主句之后，不能放在句首。而且經(jīng)常是對(duì)主句補(bǔ)充說明理由或推斷原因。
如：
It rained last night, for the ground is wet.
⑤ as, when, while
這三個(gè)連詞都可引導(dǎo)時(shí)間狀語從句，但用法有所不同。
1) 當(dāng)某事正在進(jìn)行的時(shí)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(shí)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(gè)長(zhǎng)動(dòng)作同時(shí)進(jìn)行的時(shí)候，最常用的是while。例如：
While mother was cooking lunch, I was doing my homework.
3) 當(dāng)兩個(gè)動(dòng)作都表示發(fā)展變化的情況時(shí)，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(gè)短動(dòng)作同時(shí)發(fā)生時(shí)，或表示“一邊…一邊…”時(shí)，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(dòng)作先于主句的動(dòng)作時(shí)，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(dòng)作，主句是延續(xù)性動(dòng)作時(shí)，通常用when。例如：
When John arrived I was cooking lunch.
(6)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.
1) 引導(dǎo)主語從句時(shí)。例如：
Whether he will come to the party is unknown.
2) 引導(dǎo)表語從句時(shí)。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.
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