field hospital vs hospital

field hospital

noun
  • A large mobile medical unit that temporarily takes care of casualties before they can be safely transported to more permanent hospital facilities. 

hospital

noun
  • A large medical facility, usually in a building with multiple floors, where seriously ill or injured patients are given extensive medical and/or surgical treatment. 

  • A building founded for the long-term care of its residents, such as an almshouse. The residents may have no physical ailments, but simply need financial support. 

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