- diurnal - belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night"
Antonym: nocturnal
- diurnal - having a daily cycle or occurring every day; "diurnal rhythms"; "diurnal rotation of the heavens"; "the diurnal slumber of bats"
Antonyms: noncyclic, noncyclical (indirect, via cyclic)