所谓垂悬结构（The Dangling Construction）就是一个句子成分，如分词短语，不定式动词短语等，找不到被修饰的主语或被修饰的对象不合逻辑。垂悬结构是种错误的句法，应该避免。
下面是三种常见的垂悬结构及其改正方法：
⒈垂悬分词或分词短语，如：
① Climbing up the hill, several boars were seen.
这句子里的现在分词短语（present participial phrase）修饰主语several boars是错的；改正方法有二：
（a）确定是逻辑主语，使句子变成Climbing up the hill, the explorers saw several boars.
（b）把现在分词短语扩大为副词分句（也称状语从句）：When the explorers climbed up the hill, they saw several boars/ several boars were seen.
⒉垂悬副词短语，如：
② After putting a shrimp on the hook, the fish began to bite.
这句的副词短语（adverb phrase）和主语the fish有什么逻辑关系呢？真正的逻辑主语应该是the fisherman或the angler才对。改正方法和例①同：
（a） After putting a shrimp on the hook, the fisherman found that the fish began to bite.
（b） After the fisherman had put a shrimp on the hook, the fish began to bite.
⒊垂悬不定式动词短语，如：
③ To write well, a lot of practice is needed.
④ To be a loyal employee, a sense of belonging is a must.
这两个句子的不定式动词短语（infinitive phrases）并不能修饰practice和a sense of belonging，真正的主语必须是 人，如：
（a） To write well, one needs a lot of practice/a person has to practise a lot.
（b） To be a loyal employee, he or she must have a sense of belonging.
上述三类垂悬结构中，第一类发生的频率最高，必须注意。但是在下列三种情况下，分词短语是对的，它们并非垂悬结构：
第一，独立结构（The Absolute Construction，见3月7日《中英合谈》）中的分词短语有自己的主语，所以不是垂悬结构。例如：
① Such being the case, we can go home now./it is not wrong to call it a day.
第二，当分词含有介词或连词性质时，它不需要逻辑主语，所以没有垂悬问题存在。例如：
② Owing to a lack of funds, the project has to be discontinued.
③ Provided that there is sufficient time, everyone can do the job better.
第三，当分词短语是用来表示说话者的态度或意见时，也不需要逻辑主语，因此也不存在着垂悬问题。例如：
④ Judging from his facial look, the news must have been terrible.
⑤ Taken as a whole, there is nothing wrong with the logic behind that idea.