Use farther with physical distance.

用farther來表示實際的有數(shù)值的距離

If you're thinking about more miles, more kilometres, more inches, more centimetres, etc., then you almost certainly want farther.

如果你想到的更多是多少英里，公里，英寸，厘米，等等，那么你幾乎肯定要用farther

Use further with non-physical 'distance' (i.e., figurative distance).

用further來表示非實際的“距離”，指抽象的距離

If you're not thinking about more miles etc. but more time, more effort (in fact, more anything that isn't distance), then you almost certainly want further. 

如果你想到的跟數(shù)字單位那些距離都毫無關(guān)系，而是一些時間，付出等等，那么你肯定要用到的就是further。

Further is more diverse than farther. It covers all topics (even distance these days) and can mean furthermore, moreover, more, additional, extra and supplementary. 

Further比farther更加多元化，包含了很多方面（現(xiàn)在也可以表示具體的距離），就和“而且；此外（furthermore, moreover, more, additional, extra and supplementary）”這些詞一個意思。