adj.1 of or during the day; not nocturnal.
2 daily; of each day.
3 Astron. occupying one day.
4 Zool. (of animals) active in the daytime.
5 Bot. (of plants) open only during the day.
Derivatives:
diurnally adv.
Etymology: ME f. LL diurnalis f. L diurnus f. dies day