cold frame vs greenhouse

cold frame

noun
  • A transparent-roofed enclosure, built low to the ground, used to protect plants from cold weather. 

greenhouse

noun
  • A building used to grow plants, particularly one with large glass windows or plastic sheeting to trap heat from sunlight even in intemperate seasons or climates. 

  • A hot state in global climate. 

  • A structure that shields the operating table to protect against bacteria. 

verb
  • To place (plants) in a greenhouse. 

  • To nurture in order to promote growth. 

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