diurnal vs nightly

diurnal

noun
  • A flower that opens only in the day. 

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

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. 

nightly

noun
  • A build of a software program with the latest changes, released every night. 

adv
  • Every night. 

adj
  • Happening or appearing in the night; night-time; nocturnal. 

  • Performing, occurring, or taking place every night. 

  • Used in the night. 

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