1、同位语从句与前面的名词是同位关系，即说明它前面名词的内容，定语从句与前面的名词是修饰与被修饰关系，即限定它前面的名词范围，或补充一些情况
2、例如the news that I have passed the exam is true，这个是同位语从句，the news that he told me just now is true,这个则是定语从句
3、引导同位语从句的that是连词，在句中不充当任何成分，引导定语从句的that是关系代词，除了起连接作用外，还在从句中充当主语，宾语或表语等
4、例如the idea that computers can recognize human voice surprises many people此为同位语从句，the idea that he gave surprises many people此为定语从句
5、定语从句是从句对先行词的修饰或限制，属于形容词性从句的范畴，同位语从句是从句对前面抽象名词的进一步的说明和解释，属于名词性从句的范畴
6、例如I made a promise that if anyone set me free, I would make him very rich, 此为同位语从句，the mother made a promise that pleased all her children,此为定语从句
