apartment vs roof

apartment

noun
  • A complete domicile occupying only part of a building, especially one for rent; a flat. 

  • A conceptual space used for separation in the threading architecture. Objects in one apartment cannot directly access those in another, but must use a proxy. 

roof

noun
  • The external covering at the top of a building. 

  • The top external level of a building. 

  • The upper part of a cavity. 

  • An overhanging rock wall. 

  • The surface or bed of rock immediately overlying a bed of coal or a flat vein. 

verb
  • To cover or furnish with a roof. 

  • To traverse buildings by walking or climbing across their roofs. 

  • To put into prison, to bird. 

  • To shelter as if under a roof. 

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