noun

• A venue where sporting events are held.
• An Ancient Greek racecourse, especially, the Olympic course for foot races.
• (historical) Synonym of stadion, a Greek unit of length equivalent to about 185 m.
• A kind of telemeter for measuring the distance of an object of known dimensions, by observing the angle it subtends.
• (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.
• (biology) A life stage of an organism.