定语从句重、难点易错档案

一、语意重复。定语从句的引导词在从句中都要充当一定的成分，所以从句里相应的句子成分不能再保留，否则就犯了语意重复的错误。如：

The main topic people are often talking about at present is personal cars.

The main topic是先行词，关系代词that或which在从句中作宾语，被省略了，所以做宾语的替代词it不能再出现了。

二、分裂现象。如无特殊原因，定语从句应紧跟在先行词之后。如：

Everything that has weight and occupies space is called matter.

初学者很容易将此意表达成：Everything is called matter that has weight and occupies space. 这就是人为地造成的分裂现象。但是有时定语从句和先行词之间需要插入定语、状语或谓语时则另当别论。如：

There is an expression in his eyes that I cannot understand.先行词与定语从句之间被in his eyes隔开了。

三、主、谓不一致。当关系代词在从句中作主语时，从句的谓语动词应该和先行词的数与格保持一致，否则就是犯了主、谓不一致的错误。如：

God bless this ship and all that sail in her. (Bible)

本例先行词all指的是"所有的人"，所以定语从句的谓语不能用sails。

四、关系代词that、who直接置于介词后。关系代词前有介词时，关系代词必须用which（指物）或 whom (指人)，而且不能省略。如果把介词放到句子的后部去，这时关系代词可用that或who,也可以把它们省略。如：

The cost at which we produce the cars has been greatly reduced.

由于关系代词直接置于介词at之后，所以只能用which，而且不能省略。

五、关系代词作定语时的误用。不管先行词是指人还是物，关系代词在从句中作定语时，都必须用whose；但指物时，还可以用"the + 名词 + of which"或"which of its + 名词"的形式表示。如：

This is a new digital control machine tool whose functions are very advanced.

本例中的whose functions还可以用which of its functions或者the functions of which替换。

六、关系代词that的误用。先行词是以下某种情形时，必须用that引导定语从句：（1）被