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.
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.
Hear it pronounced