I. dī-ˈər-n ə l adjective
Etymology: Middle English, from Latin diurnalis — more at journal
Date: 14th century
1.
a. : recurring every day
diurnal tasks
b. : having a daily cycle
diurnal tides
2.
a. : of, relating to, or occurring in the daytime
the city's diurnal noises
b. : active chiefly in the daytime
diurnal animals
c. : opening during the day and closing at night
diurnal flowers
• di·ur·nal·ly -n ə l-ē adverb
II. noun
Date: 1600
1. archaic : diary , daybook
2. : journal 2a