region vs terrain

region

noun
  • Any considerable and connected part of a space or surface; specifically, a tract of land or sea of considerable but indefinite extent; a country; a district; in a broad sense, a place without special reference to location or extent but viewed as an entity for geographical, social or cultural reasons. 

  • A subnational region of Chile; equivalent to province. 

  • An administrative subdivision of the European Union. 

  • A subprovincial region of Quebec; the primary level subdivision; a prefecture. 

  • The inhabitants of a region or district of a country. 

  • A place in or a part of the body in any way indicated. 

  • Such a division of the city of Rome and of the territory about Rome, of which the number varied at different times; a district, quarter, or ward. 

terrain

noun
  • An area of land or the particular features of it. 

  • The surface of the earth; the ground. 

  • A single, distinctive rock formation; an area having a preponderance of a particular rock or group of rocks. 

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