Farther and further are comparative adverbs or adjectives. They are the irregular comparative forms of far. We use them to talk about distance. There is no difference in meaning between them.

The widely accepted rule is to use farther when being literal and discussing a physical distance, as in “He went farther down the road.” Further is used when discussing a more symbolic distance or to discuss a degree or extent, as in “I wanted to discuss it further, but we didn’t have time.”

Both farther and further are correct. You might think they’re synonymous, but they have different meanings and uses in English. The standard quick answer is “ farther is for physical distance, while further is for figurative distance.”

Farther and further are easy to confuse. Farther is used for physical distance (e.g., more miles). Further is used for non-physical distance (e.g., more pages), and can be used for physical distance too (i.e., the words are largely interchangeable).

Contrary to popular opinion, further and farther don't have the same meaning. Basically, further refers to something that is additional and farther refers to actual distances between objects.