replace是指两个事物之间的替代。

例：I replaced you with him as the contestant in the competition.displace是指一个事物的转移。

例：I displaced you as the contestant from this competition to that one.另外Replace还有放回原处的意思。

当然如果Displace做替代讲的话，他有新事物使被替代事物失去地位，失去作用，失去功能的意思。