同位语从句和定语从句在结构上看上去相似，都有句子修饰的先行词，所以很容易混淆。
尽管结构相似，但是从语法功能和意义上讲有明显区别。下面举例说明：
The news that our team won the match excited the whole class, including our head teacher.
(此句中that引导的从句是对news内容的解释说明，即回答了what is the news？这样的问题，另外，that在从句中不充当任何成分）
The news that he told me yesterday excited the whole class, including our head teacher.
(此句中that从句不是在解释news的内容，而且that不仅仅起引导从句的作用，同时在宾语从句中充当told的直接宾语）
再比如：
The promise that he made was very serious.(定语从句）
The promise that he will buy a gift for me is really exciting.（同位语从句）
追问谢谢了