1. that指代reason,在从句中作主语或宾语:
We do things for good reasons that are bad.
我们做事出于好的理由,但它其实是坏的。
2. why指代reason,在从句中作原因状语:
There are a lot of reasons why marriages don't continue.
婚姻无法维持有很多原因。
Maybe I am looking for the reason why I exist.
也许我在寻找我存在的理由。
That's the reason why I'm making albums. That's the reason why I love hip-hop: It's a challenge every time.
这就是我制作专辑的原因。这就是我喜欢嘻哈的原因:每次对我都是挑战。
The reason why men enter into society is the preservation of their property.
人们融入社会的原因是他们要保护财产。