在《容易犯錯的形容詞從句》一文里，知道形容詞從句總是跟在被修飾的名詞(即先行詞)后面。例如：

① Any change which causes the formation of new matters is a chemical change.(在主句主語的名詞之后)

② Plastics is an important material which is widely used in industry.(在主句補足語名詞之后)

③ It has certain features that are easily recognised.(在主句賓語名詞之后)

在下列情況下，形容詞從句和所修飾的名詞隔開：

㈠被介詞短語隔開，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里的形容詞從句和先行詞“l(fā)ines”被介詞短語“of force” 分離。⑤里的卻被另一個介詞短語“of matter”隔開。

㈡被分詞短語隔開，如：

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

⑥里的形容詞從句和先行詞“method”之間被過去分詞短語“ known to medical science today”隔開。

上述兩種隔離情況可以理解，也被接受。

另外還有一種分隔情況，也偶爾見到，特別在科技英語中，但這種離異法，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里的形容詞從句和先行詞“ideas”及“substances”之間都被主句的謂語動詞“came along”和“are known”分開。

這類的分隔情況，多在主句謂語動詞是被動語態(tài)(the passive voice)時才出現(xiàn)，如例⑧，但謂語動詞是主動語態(tài)(the active voice)的話，也可以，如例⑦，只是數(shù)量少些。

為什么要把形容詞從句常見的位置和先行詞分開呢?主要原因是：先行詞所在的主句較短，而修飾先行詞的形容詞從句則很長。為了平衡主句和從句，才采用這方法。雖然如此，但它和一般的形容詞從句的位置有很多抵觸，恐怕引起混亂。

為了減少不必要的麻煩，最好改用別的句式。其中一個方法是將形容詞從句改為另外一個獨立的簡單句(如例⑨&╆);另一個辦法是采用并列句(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.