Farther or Further ???

Farther or Further 都是副词 ( Adverb ).

Farther 是更 远Further 是进一步的意思。有鉴于此，Farther是用在来形容距离，道路的长短；Further是用于非物体性的名词。

1. Farther

We have to walk farther before we can reach our destination.

How much farther our plane has to fly to reach the airport?

2. Further

I need to explain further to make my points clear to you.

Why do you need to suggest further ?