These words are often misunderstood and misused by native English speakers.Both words are used to say “more far”, which of course is grammatically incorrect.The quick and easy tip is to use “farther” for physical distance and “further” for metaphorical, or figurative, distance. It’s easy to remember because “farther” has the word “far” in it, and “far” obviously relates to physical distance.
Here are two examples: A) An impatient child in the backseat of a car keeps asking her mother, “Mom, how much farther is it to the beach?” – She uses “farther” because she is talking about a physical distance.
B) The same mother may become frustrated and reply, “If you complain any further, I’ll take you straight home.” – The mother uses further because she is talking about a figurative distance, the extent of the child’s complaining.