Also found in: Thesaurus, Medical, Legal, Encyclopedia, Wikipedia.


1. Relating to or occurring in a 24-hour period; daily.
2. Occurring or active during the daytime rather than at night: diurnal animals.
3. Botany Opening during daylight hours and closing at night.
1. A book containing all the offices for the daily canonical hours of prayer except matins.
2. Archaic
a. A diary or journal.
b. A daily newspaper.

[Middle English, from Late Latin diurnālis, from Latin diurnus, from diēs, day; see dyeu- in Indo-European roots.]

di·ur′nal·ly adv.
References in classic literature ?
in imitation of the tone in which that useful class of society are wont, diurnally, to make their presence known at area railings.
The number of wild fish detected peaked during daylight hours, indicating that the fish were diurnally active.
It can also be manually adjusted and automatically operated in a diurnally controlled light cycle when selected by the user.
Nevertheless, because scavenged carcasses were consumed diurnally and nocturnally, and human surveys for carcasses were largely conducted diurnally, our study supports prior assertions that failure to account for removal of carcasses by scavengers might bias studies toward lower estimates of mortality (Dwyer and Mannan, 2007; Ponce et al.
Among fireflies, direct evidence for volatile pheromones in sexual communication has thus far been restricted to diurnally active species (De Cock & Matthysen 2005; Lloyd 1972, 1997b; Ohba 2004).
mosquitoes are diurnally active, which indicates that long-lasting insecticide-treated bed nets are ineffective for dengue vector control (17,55,56.
About twice as large as our American mink, chunkier and noticeably redder, they swam visibly, diurnally hunting for seabirds, eggs and shellfish.
Fifth, hematologic and biochemical results may vary seasonally, monthly, or diurnally, as well as by age, sex, or time of day.
As we were interested in determining the degree to which birds vocalize diurnally and seasonally, we used the total number of detections as our response variable.
striata shows nectar production and high visitation rates diurnally (Rocha et al.
It has a humid subtropical climate with a temperature variation of barely 20 degrees diurnally.