The parasang (Persian فرسنگ farsang) is an ancient Persian unit of itinerant distance, sometimes referred to as a schoenus, was extremely variable but usually corresponded to approximately 3.5 miles (5.6 kilometers), or the distance that could be traversed on foot in an hour.
Some, but certainly not all, measurements of distances in antiquity (and even today) are quite variable. In particular, distances used by caravan leaders tend to vary considerably and are often more a rough measurement of the time it took to cover a certain portion of a route. Thus, they tended to be longer when travalling over flat, even ground, and shorter in mountainous country.
Also, of course, measurements of distance tend to vary from time to time and place to place, and according to the uses they are put to. For example, compare the Roman mile, the Imperial or English mile, and the Nautical mile.
Wilfred H. Schoff notes:
SUMMARY. The SCHOENUS or Parasang was a Persian measure, perhaps not altogether fixed, and may be calculated as somewhere between 3¼ and 3½ miles; more or less, perhaps, an hour’s travel by caravan. According to Strabo, it was equal to 40 stadia, but varied from 30 to 60.
(Strabo XV, I, II.) “When I ascended the hills, the measures of these schoeni were not everywhere uniform, so that the same number sometimes designated a greater, sometimes a less actual extent of road, a variation which dates from the earliest time and exists in our days.”
Masson notes Isidore’s schoenus in Persia was about 2½ miles; on the Euphrates, 3¼. Cf. Herodotus I, 66.
parasang in Modern Greek (1453-): Παρασάγγης
parasang in French: Parasang
parasang in Italian: Parasanga
parasang in Japanese: パラサング
parasang in Polish: Parasanga
parasang in Portuguese: Parasanga
parasang in Russian: Парасанг