- of or relating to a day or each day; daily.
- of or belonging to the daytime (opposed to nocturnal).
- Botany. showing a periodic alteration of condition with day and night, as certain flowers that open by day and close by night.
- active by day, as certain birds and insects (opposed to nocturnal).
- Liturgy. a service book containing offices for the daily hours of prayer.
- Archaic. a diary.
- Archaic. a newspaper, especially a daily one.
- happening during the day or daily
- (of flowers) open during the day and closed at night
- (of animals) active during the dayCompare nocturnal
- a service book containing all the canonical hours except matins
late 14c., from Late Latin diurnalis “daily,” from Latin dies “day” + -urnus, an adjectival suffix denoting time (cf. hibernus “wintery”). Dies “day” is from PIE root *dyeu- “to shine” (cf. Sanskrit diva “by day,” Welsh diw, Breton deiz “day;” Armenian tiw; Lithuanian diena; Old Church Slavonic dini, Polish dzień, Russian den), literally “to shine” (cf. Greek delos “clear;” Latin deus, Sanskrit deva “god,” literally “shining one;” Avestan dava- “spirit, demon;” Lithuanian devas, Old Norse tivar “gods;” Old English Tig, genitive Tiwes, see Tuesday).
- Having a 24-hour period or cycle; daily.
- Occurring or active during the daytime rather than at night.
- Occurring once in a 24-hour period; daily.
- Having a 24-hour cycle. The movement of stars and other celestial objects across the sky are diurnal.
- Most active during the daytime. Many animals, including the apes, are diurnal.
- Having leaves or flowers that open in daylight and close at night. The morning glory and crocus are diurnal. Compare nocturnal.