Farther vs. Further

It is common to use farther and further interchangeably. They both have similar meaning; however, there are subtle differences in their usage.

Farther is used to describe or discuss physical distances.

Example: Susie walked farther down the road.

Further is used  to discuss degree or extent or figurative distance.

Example:  Susie wanted to discuss the issues further.

Both can be used interchangeably  in a situation where one can be referring to either physical distances or figurative distances.  

Example: Susie is further vs farther along in her book reading than Lucie.

In this case, Susie can be referring either to physical book pages (farther) or through the story content of the book (further).

Other tidbits:

One can apply further in places of advancing something like a project.

Further can be used in place of moreover or additionally as in “further, you took my belongings”… 

It is common to see furthermore used as well ….

Take home lesson:

 So, which one do you use when you interrupt someone in the middle of a sentence? Is it “before you go any further, or “before you go any farther”? It depends on If you are referencing physical or measurable distance (or advancing of) or figurative distance (degree/extent of). General rule is when in doubt, it is safer to use further as farther tends to carry more restrictions.

“With persistence, I will go farther to further my goals”.