4、 表示转折关系，连接的双方构成对比，意义上有转折。常用连词有but, however, while, only
例如：
a) His brother is fond of football while he likes basketball.
b) You can watch TV, but you must finish your homework first.
3、 表示选择关系的连词，连接的双方只取其一。常用连词有or, either...or, otherwise
a) You can go to Beijing either today or tomorrow.
b) You must get up early or you won’t catch the early bus.
2、 介词和动词、形容词、名词等常常构成固定搭配，也就是说，在这些词的后面常常要求用一定的介词。这一点在学习时要特别注意。如： a.动词+介词：laugh at, wait for b.形容词、过去分词+介词：be good at, be proud of
c名词+介词：pay a visit to , the key to
1、介词一般放在名词之前，但它后面的介词宾语是疑问代词、疑问副词或者关系代词时，这些词提到了前面而只剩下介词在后了。
第二节 实战演练
4.though (although)引导让步状语从句，because 引导原因状语从句， 所以though(although)不能和并列连词but ，because 不能和并列连词 so一起使用。只能单独使用。
3.从属连词引导的从句不可以与主句断开。
例如：When the alarm clock rang. (不完整)
2.从属连词，如that, whether, when, because, though等，用以引导名词性从句、定语从句和状语从句。
(一)并列连词和从属连词的用法
连词按其性质可分为：
1.并列连词，如：and, or, but, so for, 等， 连接并列的词与词，短语与短语，句子与句子。
例如：Rice and potatoes are common foods. (词与词)
Today we can travel by plane or by train. (短语与短语)
Many trees lose their leaves in winter, but evergreen trees do not. ( 句子与句子)
关联连词是一类成对使用的连词
例如：both……and……, not……but…….
not only……but also…… not only…but… as well
either……or…… neither……nor……
关联连词必须后接同样的语法结构。
如：Either the windows or the door was open .
(四)常用介词用法比较
(1)as , like
as 表示“作为”强调身份，like (介词)表示“像”
As a teacher, he cares for these children.
Like a teacher, he cares for these children.
(2)with , in
with 表示“外貌特征或附带的东西” ,“ 用……作工具”
in 表示”衣着” ，用某语言，也用in
A man with dark glasses wanted to buy drinks.
A man in black wanted to buy drinks.
The boy is learning to write in pencil / with a pencil.
He retold the text in English.
(3)for , to
for表示“为了.”
to 表示动作对象, “对, 向”， 如:
He would do anything for his motherland.
Did you mention this to my father?
你对我父亲提起过这件事吗?
for 表示“就某情况而说 ”, to 表示“对某对象而言”如：
It’s quite warm today for February.就二月的天气，今天够暖和的。
What he told you just now was not new to me。
他刚才对你所说的话对我并不新鲜。
for 表示“目的,用途”。与go, come 动词连用。
(4)except , besides
except 表示“从总体中排除一部分”, 与but 同义， besides 表示“除了一部分还有另一部分”
We all failed except him. 我们都失败了，但他没有。
He speaks German besides French.. 除法语外， 他还会讲英语。
(5)注意成对介词的用法：
get into (out of ) the car, jump onto (off) the platform, out of
(6)介词和名词动词等有不少固定搭配和习惯用法：
to one’s surprise / joy, in charge of , instead of, in bed (hospital), in trouble, in a hurry, in surprise, with a smile, with one voice, according to, at once, on time, in time, in all, at last, at least, in the end, by the way, for example, at the same time, at the same speed, on one’s way (to), in the sun, on the football team, in line, with the help of, in red / green ，put on, look for, look after, run after, send for, enter for, pay for, show…around, listen to, arrive in / at, get to, agree with, succeed in, think of (about), wait for,…