A traditional unit of distance. Derived from an ancient Celtic unit and adopted by the Romans as the leuga, the league became a common unit of measurement throughout western Europe. It was intended to represent, roughly, the distance a person could walk in an hour. The Celtic unit seems to have been rather short (about 1.5 Roman miles, which is roughly 1.4 statute miles or 2275 meters), but the unit grew longer over time. In many cases it was equal to 3 miles, using whatever version of the mile was current. At sea, the league was most often equal to 3 nautical miles, which is 1/20 degree [2], 3.45 statute miles, or exactly 5556 meters. In the U.S. and Britain, standard practice is to define the league to be 3 statute miles (about 4828.03 meters) on land or 3 nautical miles at sea. However, many occurrences of the "league" in English-language works are actually references to the Spanish league (the legua), the Portuguese league (legoa) or the French league (lieue). For these units, see below on this page. In the classic Jules Verne novel Twenty Thousand Leagues under the Sea (Vingt Mille Lieues sous les Mers) the unit in the title is the French metric lieue, equal to exactly 4000 meters