一同位语和定语的区别、同位语从句与定语从句的相似之处
e.g. The news that our team has won the final match is encouraging. （同位语从句）
我们队取得决赛胜利的消息令人鼓舞。
The news that you told us is really encouraging.（定语从句）
你告诉我们的消息真的令人鼓舞。
2、两种从句都可以用that引导
e.g. The suggestion that students should learn something practical is worth considering. （同位语从句）
学生应该学些实用的东西的建议值得考虑。
The suggestion that is worth considering is that the students should learn something practical.（定语从句）
值得考虑的建议是学生应该学些实用的东西。
二、同位语从句与定语从句的不同之处
1、从句的作用不同：同位语从句用来进一步说明前面名词的内容；定语从句用来修饰、限定前面的名词。
e.g. The news that our team has won the final match is encouraging. （从句说明“消息”的内容：我们队取得了决赛胜利。）
The news that you told us is really encouraging.（从句对“消息”加以限定：是你告诉我们的，而非来自其他渠道。但消息是何内容却不得而知。）
2、引导从句的关联词that的功能不同：that引导同位语从句时是一个纯连词，不充当任何成分；而引导定语从句的that是关系代词，既指代先行词又须在从句中充当成分。
e.g.1) Dad made a promise that he would buy me CD player if I passed the English test. （that 不充当任何成分）
2) Dad made a promise that excited all his children.（that指代promise，又在从句中充当主语。）
3、that引导同位语从句时是一个纯连词，故不能用which替换；而that引导定语从句时是代词，常可以和另一关系代词which替换。
e.g. The fact that he is from Canada is new to me. （that不可换为which）
The fact that surprised me is that he is not Chinese.（第一个that可换为which，第二个不行，因为它引导的是表语从句。）
4、引导同位语从句关连词，除that外，还可以根据句义使用任何其它疑问代词或副词；而定语从句不可用what, how, whether等引导。
e.g. I had no idea at all what I should do next.
There is no proof whether he was killed by others.
不定式做同位语和定语如何区分
不定式做定语时与其所修饰的名词通常是主谓或动宾关系。例如：The next train to arrive was from Beijing. 下一列到站的火车是从北京开来的。（主谓关系）
It was a game to remember. 那是一场令人难忘的球赛。（动宾关系）
不定式做同位语时只是去解释前面名词的内容，绝无上述两种关系。例如：He gave the order to start the attack. 他下达了开始进攻的命令。（to start …与the order 同位）
