现在分词和动名词的区别

这种考法在句子改错中考查的并不多。原因很简单，现在分词和动名词通常不充当相同的成分，动名词一般充当主干，分词充当修饰，谁也不干预谁。但是，有一种情况会让两者重叠，即， 当介词短语做状语时，其有可能和现在分词短语做伴随状语出现同成分的情况，例如：

(1) By using a pen, I wrote a book.
(2) **Using a pen, I wrote a book. 

两个例句的划线部分，句(1)的using a pen是一个动名词短语，句(2)中其是一个现在分词短语。那么，这样的两者应该怎么判断呢？实际上，"Using" 是隐含的, 在句中的 "using" 确有 "by using" 的意思, 但这不代表 "using" 就一定是 "by using". "using" 其实只是把两句联系起来, 而没有把他们的关系明确指出. 以下有两句例句, 会更明显:

(a) Using his trendy hair gel again, John created yet another brilliant hair style.
(b) Using his trendy hair gel again, John got punished by the disciplinary teacher.

两者都是隐含写法, 但根据语意, 显然地：

在 (a), John 是通过 "Using his trendy hair gel again" 这方法来 "created yet another brilliant hair style"
在 (b), John 是因为 "Using his trendy hair gel again" 而导致 "got punished by the disciplinary teacher. , 而不是通过的方法.

所以在这情况下, (a) 也可以写成:

By using his trendy hair gel again, John created yet another brilliant hair style.

而 (b) 是:

Because of using his trendy hair gel again, John got punished by the disciplinary teacher.
(而不是 "By using")

总括而言, "Using" 和 "By using" 是写作手法上的分别。如果用了using，表明主从句实质上是因果关系，如果用了by using，表明主从句实质上是方式关系，例如(1)(2)两个例句，我们只能用(1)而不能用(2)，这是因为，我们不能说：
因为用钢笔，所以我写了一本书。