diurnal vs nocturnal

diurnal

adj
  • Happening or occurring during daylight, or primarily active during that time. 

  • Said of a flower open, or releasing its perfume during daylight hours, but not at night. 

  • Done once every day; daily, quotidian. 

  • Having a daily cycle that is completed every 24 hours, usually referring to tasks, processes, tides, or sunrise to sunset; circadian. 

noun
  • A flower that opens only in the day. 

  • A book containing canonical offices performed during the day, hence not matins. 

nocturnal

adj
  • Taking place at night, nightly. 

  • Primarily active during the night. 

noun
  • A device for telling the time at night, rather like a sundial but read according to the stars. 

  • A person or creature that is active at night. 

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