Webster's Revised Unabridged Dictionary · 1913

Diurnal

Diurnal , a.

[L. diurnalis, fr. dies day. See Deity, and cf. Journal.]

1.
Relating to the daytime; belonging to the period of daylight, distinguished from the night; -- opposed to nocturnal; as, diurnal heat; diurnal hours.
2.
Daily; recurring every day; performed in a day; going through its changes in a day; constituting the measure of a day; as, a diurnal fever; a diurnal task; diurnal aberration, or diurnal parallax; the diurnal revolution of the earth.
Ere twice the horses of the sun shall bringb Their fiery torcher his diurnal ring. — Shakespeare
3.
Opening during the day, and closing at night; -- said of flowers or leaves.
4.
Active by day; -- applied especially to the eagles and hawks among raptorial birds, and to butterflies (Diurna) among insects.

Diurnal , n.

[Cf. F. diurnal a prayerbook. See Diurnal, a.]

1.
A daybook; a journal.
2.
A small volume containing the daily service for the “little hours,” viz., prime, tierce, sext, nones, vespers, and compline.
3.
A diurnal bird or insect.