farthest

(comparatives of `far') most remote in space or time or order; "had traveled to the farthest frontier"; "don't go beyond the farthermost (or furthermost) tree"; "explored the furthest reaches of space"; "the utmost tip of the peninsula"

to the greatest distance in space or time (`farthest' is used more often than `furthest' in this physical sense); "see who could jump the farthest"; "chose the farthest seat from the door"; "he swam the furthest"

to the greatest degree or extent or most advanced stage (`furthest' is used more often than `farthest' in this abstract sense); "went the furthest of all the children in her education"; "furthest removed from reality"; "she goes farthest in helping us"