Farther or Further?
Your choice!
Farther
Exemple : ‘’She moved farther down the train to sit with her friends.’’
The words “farther” and “further” can be used interchangeably to mean something is “at, to, or by a greater distance.”
Further
Exemple : ‘’You have gone further than any of your colleagues.’’
Although the two words can be used interchangeably and have the same meaning it is far more common to use the word “further,” which is also used in set expressions such as “without further delay.”