为什么how不能引导定语从句

为什么how不能引导定语从句

有些学生认为，how可以作为关系副词引导定语从句。这是一种比较普遍的错误说法。其实，在现代英语中，how不能用作关系副词，不用来引导定语从句。当定语从句的先行词是"the way"时,并且关系词在从句中作状语,那么关系词可以用下列三种形式: (1)that (2)in which (3)省略引导词。 如：
That is the way that he spoke.(正确）
That is the way in which he spoke. （正确）
That is the way he spoke .(正确）
That is the way how he spoke .（错误)
但可以说： That is how he spoke.（这里的how he spoke属于名词性从句之中的表语从句）

关系副词在美国英语里只有三个：when、where、why。它们引导定语从句，在从句中作的是状语。
when引导定语从句，在从句里作时间状语，先行词表示时间。如：
Tuesday is the day when the garbage truck comes.
where引导定语从句，在从句里作地点状语，先行词表示地点，如：
I once again came to New York, where I hadn't been for ten years.
He and his family moved to Italy, from where he moved to Germany and went to university.
He has reached a point where a change is needed.
why引导定语从句，在从句中作原因状语，先行词只有reason。
That's the reaon why I didn't go to college.
how不能引导定语从句，它可以作疑问副词或缩合连接副词使用。如果先行词是the way，则可以用in which、that引导定语从句。如：
I don't know how I can solve the problem.
That is how he solved the problem.
That is the way in which/that he solved the problem