FURTHER or FARTHER
Further refers to a time or an amount. It is a metaphorical or figurative distance.
Additional . additionally . a greater degree
Additional . additionally . a greater degree
- This book needs further work done to it.
- I am further along in my book than the rest of the class.
Farther refers to length and distance. It's a physical distance.
- Spain is farther south than France.
- I shall be moving farther from the city in June.