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。

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

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

例如：

a) You can go to Beijing either today or tomorrow.

b) You must get up early or you won’t catch the early bus.

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.

5、 表示联合关系，联合的双方是对等的，意义上趋向一致。常用连词有：and, both...and, neither...nor, not only...but also, as well as

To study English well, we need both diligence and careful.

That horse is not only the youngest among the five, but also runs the fastest.

6、 表示因果关系，连接的双方，互为因果，或者前因后果，或者前果后因。常用的连词有：for, so

例如：

It must have rained, for the ground is wet.

【考点诠释】