Di*ur"nal (?), 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 bring
Their fiery torcher his diurnal ring.
Shak.
3. (Bot.) Opening during the day, and
closing at night; -- said of flowers or leaves.
4. (Zoöl.) Active by day; --
applied especially to the eagles and hawks among raptorial birds, and
to butterflies (Diurna) among insects.
Diurnal aberration (Anat.), the
aberration of light arising from the effect of the earth's rotation
upon the apparent direction of motion of light. --
Diurnal arc, the arc described by the sun
during the daytime or while above the horizon; hence, the arc
described by the moon or a star from rising to setting. --
Diurnal circle, the apparent circle described
by a celestial body in consequence of the earth's rotation. --
Diurnal motion of the earth, the motion of the
earth upon its axis which is described in twenty-four hours. --
Diurnal motion of a heavenly body, that
apparent motion of the heavenly body which is due to the earth's
diurnal motion. -- Diurnal parallax. See
under Parallax. -- Diurnal revolution of a
planet, the motion of the planet upon its own axis
which constitutes one complete revolution.
Syn. -- See Daily.
Di*ur"nal (?), n. [Cf. F.
diurnal a prayerbook. See Diurnal,
a.] 1. A daybook; a
journal. [Obs.] Tatler.
2. (R. C. Ch.) A small volume
containing the daily service for the "little hours," viz., prime,
tierce, sext, nones, vespers, and compline.
3. (Zoöl.) A diurnal bird or
insect.
