This chapter explains the difference between "further" and "farther" in American English, noting that "farther" is used for physical distance and "further" for metaphorical distance. However, it also clarifies that this distinction isn't strictly followed and that using them interchangeably is often acceptable, especially in ambiguous cases or in British English.
In American English, "farther" refers to physical distance, while "further" denotes metaphorical distance.
This distinction is not always strictly observed; using the words interchangeably is often acceptable.
In British English, both "further" and "farther" are used for physical distance.