Greek στάδιον. Literally "a racecourse". Also called Furlong, Stade, Stadia.
The Greek furlong, about 185 m — the length of a running track, and the unit the New Testament gives distances in.
Length
176–192 m (577–630 ft).
Reckoned from surviving stadia at Olympia, Delphi and Epidaurus.
Greek cities did not agree on it. The Attic stadion of about 185 m is the usual reckoning for the New Testament.
A stadion is the length of the footrace at Olympia, and it became the standard Greek distance unit: about 185 m, or roughly 600 feet. Older English versions translate it "furlong", which is close enough at 201 m to be confusing. It is how John measures the distance from Jerusalem to Bethany, and how Revelation gives the dimensions of the new Jerusalem.
The stadion was the length of the footrace at Olympia, and it became the Greek unit of distance. Bethany is fifteen stadia from Jerusalem (John 11:18), and Emmaus sixty (Luke 24:13): 10.6–11.5 km (6.56–7.16 miles), a long afternoon’s walk.