在《容易犯错的形容词从句》一文里，知道形容词从句总是跟在被修饰的名词(即先行词)后面。例如：

① Any change which causes the formation of new matters is a chemical change.(在主句主语的名词之后)

② Plastics is an important material which is widely used in industry.(在主句补足语名词之后)

③ It has certain features that are easily recognised.(在主句宾语名词之后)

在下列情况下，形容词从句和所修饰的名词隔开：

㈠被介词短语隔开，如：

④ Magnets work through lines of force that extend between the two ends of the magnet.

⑤ A molecule may be defined as the smallest particle of matter that can exist without changing its nature.

④里的形容词从句和先行词“lines”被介词短语“of force” 分离。⑤里的却被另一个介词短语“of matter”隔开。

㈡被分词短语隔开，如：

⑥ There is no method known to medical science today that can effectively cure cancer.

⑥里的形容词从句和先行词“method”之间被过去分词短语“ known to medical science today”隔开。

上述两种隔离情况可以理解，也被接受。

另外还有一种分隔情况，也偶尔见到，特别在科技英语中，但这种离异法，值得商榷。

例如：

⑦ Several other ideas came along that enabled engineers to design still smaller units.

⑧ Ninety-six substances are known which chemists consider to be elements.

⑦和⑧里的形容词从句和先行词“ideas”及“substances”之间都被主句的谓语动词“came along”和“are known”分开。

这类的分隔情况，多在主句谓语动词是被动语态(the passive voice)时才出现，如例⑧，但谓语动词是主动语态(the active voice)的话，也可以，如例⑦，只是数量少些。

为什么要把形容词从句常见的位置和先行词分开呢?主要原因是：先行词所在的主句较短，而修饰先行词的形容词从句则很长。为了平衡主句和从句，才采用这方法。虽然如此，但它和一般的形容词从句的位置有很多抵触，恐怕引起混乱。

为了减少不必要的麻烦，最好改用别的句式。其中一个方法是将形容词从句改为另外一个独立的简单句(如例⑨&╆);另一个办法是采用并列句(如例⑩&╇)：

⑨ Several other ideas came along. Such ideas /They enabled engineers to design still small units.

⑩ Several other ideas came along and these ideas enabled engineers to design still small units.

╆ Ninety-six substances are known. Chemists consider them to be elements.

╇ Ninety-six substances are known and chemists consider them to be elements.