名人教英文：dangling modifiers垂悬修饰语
modifier（修饰语）是用来修饰句中其他部分的字词、短语或子句，其中一类用以修饰名词，这类修饰语包括形容词、形容词短语和形容词子句，例如：
‧形容词：beijing national stadium is an impressive building.
‧形容词短语：opened in 2008, beijing national stadium has hosted a lot of major sports events.
‧形容词子句：beijing national stadium, which was opened in 2008, has hosted a lot of major sports events.
第二句把形容词短语放在句首，这个句型相当常见，但不少人运用此句型时会犯一个错误，就是没有把修饰语和正确的修饰对象连在一起。这种错误叫dangling modifiers（垂悬修饰语／不连结的修饰语）。例如：
（错误）once identified, we can fix the problem quickly.
这句主语是we，但前面的once identified（一被识别出来）不是用来形容we，而是用来形容the problem。改写这句的方法有两个：
（正确）将主语改成the problem：once identified, the problem can be fixed quickly.
（正确）将形容词短语改写成有清楚主语的副词子句：once the problem has been identified, we can fix it quickly.
再举一例：
（错误）to get a better grade, my essay has been revised twice.
想要取得更好成绩的理应是i，而不是my essay。此外，这句用了passive voice，没有清楚交代是谁修改了文章，语意含糊，并不理想。因此，这句应该改为：
（正确）to get a better grade, i have revised my essay twice.
最后一例：
（错误）after re-elected as us president, obama's opponents continued to attack his healthcare reform package.
连任总统的是obama，可是这句的主语并非obama，而是obama's opponents。正确写法是：
（正确）after obama was re-elected as us president, his opponents continued to attack his healthcare reform package.
总括而言，只要记住句首的形容词短语是用来修饰句子的主语，就可避免这类错误。