Definitions of farthest:

• adjective:   most distant or remote

  Example: "Man's farthest goal"

• adjective:   (comparatives of `far') most remote in space or time or order

  Example: "Had traveled to the farthest frontier"

• adverb:   to the greatest distance in space or time (`farthest' is used more often than `furthest' in this physical sense)

  Example: "See who could jump the farthest"

• adverb:   to the greatest degree or extent or most advanced stage (`furthest' is used more often than `farthest' in this abstract sense)

  Example: "She goes farthest in helping us"