Definition from Wiktionary, the free dictionary
diurnal (not comparable)
- Happening or occurring during daylight, or primarily active during that time.
- Most birds are diurnal.
- (botany) Said of a flower open, or releasing its perfume during daylight hours, but not at night.
- Having a daily cycle that is completed every 24 hours, usually referring to tasks, processes, tides, or sunrise to sunset.
- (uncommon) Done once every day; daily, quotidian.
- (archaic) Published daily.
- For usage examples of this term, see the citations page.
- (having a daily cycle): circadian (biology)
Coordinate terms 
- (active or open during the day): crepuscular
happening during daylight; primarily active during the day
botany; of flowers open or releasing perfume during the day
having a daily cycle
done once every day
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
Translations to be checked
diurnal (plural diurnals)
- A flower that opens only in the day.
- (Catholicism) A book containing canonical offices performed during the day, hence not matins.
- (archaic) A diary or journal.
- (archaic) A daily news publication.
A flower that opens during the day