"入乡随俗"的英文表达是 "When in Rome, do as the Romans do". 这个短语的来源可能源自一个古老的谚语，即 "Roma locuta, causa finita"，意思是 "罗马已经说了，案子就这么定了"。这个谚语暗指在罗马，人们应该遵守罗马人的习俗。

这个短语被广泛用来指导人们在旅游或到访其他文化背景不同的地方时，应该遵守当地的风俗习惯。例句如下：

- When I was in Japan, I tried to do as the Romans do and took off my shoes before entering someone's house.

- When in Rome, do as the Romans do. If you're visiting a country with a different culture, try to respect their customs.

- It's important to remember that when in Rome, you should do as the Romans do. Don't try to impose your own cultural norms on others.