The reason (why) she succeeds is obvious.
Give me one good reason (why) I should help you.
The reason (why) he did it is unknown.
The reason why we are holding this meeting is to meet each other.
There are two main reasons why I think it's the best solution.
Did you know the reason why she suddenly changed?
There are several reasons why she isn't fond of Tom.
2. why经常可与for which替换使用
This is the reason why I quit my job. 这就是我辞职的原因。
= This is the reason for which I quit my job.
以上就是定语从句why的用法和例句总结，希望对你有所帮助。你可能也需要进一步学习：the reason why和the reason that区别