Relating to the daytime; belonging to the period of daylight, distinguished from the night; -- opposed to nocturnal; as, diurnal heat; diurnal hours.
- Relating to or occurring in a 24-hour period; daily.
- Occurring or active during the daytime rather than at night: diurnal animals.
- Botany Opening during daylight hours and closing at night.
- A book containing all the offices for the daily canonical hours of prayer except matins.
- Archaic A diary or journal.
- Archaic A daily newspaper.