我查了一下好像，兩者很多時候是INTERCHANGEABLE，似乎FURTHER用法更廣。

我不太追究語法，隻是聽著別人說哪個就用哪個。下麵是我SEARCH來的信息。似乎FURTHER有時不能用FARTHER代替。

The Bottom Line

Many English speakers use both farther and further to mean "more far" in space, but only further can be used for non-physical distance and to mean "more." If you are talking about actual distance, you can usually use either word without raising any eyebrows, but keep further in mind for all of your English furthering efforts.