The parasang is a historical Iranian unit of walking distance, the length of which varied according to terrain and speed of travel. The European equivalent is the league. In modern terms the distance is about 3 or 3½ miles (4.8 or 5.6 km). Historical usage The parasang may have originally been some fraction of the distance an infantryman could march in some predefined period of time. Mid-5th-century BCE Herodotus (v.53) speaks of [an army] traveling the equivalent of five parasangs per day. In antiquity, the term was used throughout much of the Middle East, and the Old Iranian language from which it derives can no longer be determined (only two—of what must have been dozens—of Old Iranian languages are attested). There is no consensus with respect to its etymology or literal meaning. In addition to its appearance in various forms in later Iranian languages (e.g. Middle Persian frasang or Sogdian fasukh), the term also appears in Greek as parasangēs (), in Latin as , in Hebrew as parasa (), in Armenian as hrasakh (), in Georgian as parsakhi, in Syriac as parsḥā (), in Turkish as , and in Arabic as farsakh (). The present-day New Persian word is also farsakh (), and should not be confused with the present-day farsang (), which is a metric unit. The earliest surviving mention of the parasang comes from the mid-5th-century BCE Herodotus (Histories ii.6, v.53, vi.42), who defines the measure to be equivalent to 30 stadia, or half a schoenus. A length of 30 stadia is also given by several later Greek and Roman writers (10th-century Suidas and Hesychius, 5th/4th-century BCE Xenophon Anab. ii.2.6). The 6th-century AD Agathias (ii.21) however—while referring to Herodotus and Xenophon—notes that in his time the contemporary Persians considered the parasang to have only 21 stadia. Strabo (xi.xi.5) also notes that some writers considered it to be 60, others 40, and yet others 30. In his 1st-century Parthian stations, Isidore of Charax "evidently [used for schoenus] the same measure as the Arabic parasang (while in Persia proper 4 sch[onii] equal 3 par[asang])." The 1st-century Pliny (Natural History vi.26) noted that the Iranians themselves assigned different lengths to it. The Bundahishn (GBd XXII), a 9th/10th-century text of Zoroastrian tradition, glosses Avestan language hathra as equivalent to a "parasang of 1000 paces" (a Roman mile), and then defines the parasang as the distance at which a man with good eyesight