diurnal UK /daɪˈɜːnəl/US /daɪˈɝ.nəl/adjective 5noun 4forms 1 adjective5 •Happening or occurring during daylight, or primarily active during that time.Most birds are diurnal. •Said of a flower that is open, or releasing its perfume during daylight hours, but not at night. •Having a daily cycle that is completed every 24 hours, usually referring to tasks, processes, tides, or sunrise to sunset; circadian. •Done once every day; daily, quotidian. •(no longer used) Published daily. noun4 •A flower that opens only in the day. •A book containing canonical offices performed during the day, hence not matins. •(no longer used) A diary or journal.He was by birth, some authors write, / A Russian, some a Muscovite, / And 'mong the Cossacks had been bred, / Of whom we in diurnals read. — 1663 •(no longer used) A daily news publication. formsdiurnals
