the reason that和the reason why什么区别、怎么用?

the reason (why.../that...) 构成的句子都是在解释某种原因,语法上不同,但造句时经常可以混用.请看下面两个例句,仔细体会其中差别：The reason why I'm late is that/because I missed the bus. 我迟到的原因是没赶上公共汽车. （why引导原因状语从句）We aren't going, for the simple reason that we can't afford it. 我们不去, 原因很简单: 我们负担不起. （that引导同位语从句,且不能省略）