\Sta"di*um\, n.
A modern structure, with its inclosure, resembling the
ancient stadium, used for athletic games, etc.

\Sta"di*um\, n.; pl. {Stadia}. [L., a stadium (in sense
1), from Gr. ?.]
1. A Greek measure of length, being the chief one used for
   itinerary distances, also adopted by the Romans for
   nautical and astronomical measurements. It was equal to
   600 Greek or 625 Roman feet, or 125 Roman paces, or to 606
   feet 9 inches English. This was also called the {Olympic
   stadium}, as being the exact length of the foot-race
   course at Olympia. --Dr. W. Smith.
2. Hence, a race course; especially, the Olympic course for
   foot races.
3. A kind of telemeter for measuring the distance of an
   object of known dimensions, by observing the angle it
   subtends; especially (Surveying), a graduated rod used to
   measure the distance of the place where it stands from an
   instrument having a telescope, by observing the number of
   the graduations of the rod that are seen between certain
   parallel wires (stadia wires) in the field of view of the
   telescope; -- also called {stadia}, and {stadia rod}.