playing field vs stadium

playing field

noun
  • A field on which a game, especially a ball game, is played. 

  • Any place or context within which competitive activity takes place, such as market competition between companies. 

stadium

noun
  • A venue where sporting events are held. 

  • 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. 

  • 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. 

  • A life stage of an organism. 

  • An Ancient Greek racecourse, especially, the Olympic course for foot races. 

How often have the words playing field and stadium occurred in a corpus of books? (source: Google Ngram Viewer )