在一个句子中，修饰语必须清楚地修饰句中某个词或短语，如果它不修饰句中的任何成分，而处于悬浮状态，这样的修饰语即为悬垂结构。分词短语在句子中作状语时，其逻辑主语应是整个句子的主语；如果不是，而且其本身也不带自己的主语，就被认为是一个语言失误，这个分词就叫做悬垂分词。
悬垂分词例题：
误：Being Sunday,they went for a picnic.
正：It being Sunday,they went for a picnic.
悬垂不定式例题：
误：To swim properly,a course of instruction was necessary.
正：To swim properly,one needs a course of instruction.
悬垂简式从句例题：
误：When a middle school student,his parents were very strict with him.
正：When he was a middle school student,his parents were very strict with him.
