I. (ˈ)dī|ərn ə l, -|ə̄n-, -|əin- adjective
Etymology: Middle English diurnall, from Latin diurnalis — more at journal
1.
a. : repeated or recurring every day : daily
the diurnal round of tasks and cares
b. : going through its changes in a day ; specifically : having a recurrent daily cycle of change
diurnal rotation of the heavens — D.J.Price
2.
a. : performed in or belonging to the daytime
black bats, inverted in diurnal slumber — P.M.Hubbard
the city's diurnal noises faded with the night
b. : chiefly active during the daytime
hunting dogs are mainly diurnal animals — James Stevenson-Hamilton
— compare nocturnal
3. of a flower
a. : opening during the day and closing at night
b. : lasting only a day : ephemeral
4. of a sign of the zodiac : uneven
the 1st, 3d, and 5th are diurnal signs
• di·ur·nal·ly - ə lē, - ə li adverb
II. noun
( -s )
1. obsolete : a small volume containing the services for the canonical hours which are said in the daytime
2. archaic : daybook , diary
3. archaic : a daily newspaper or journal