資料來源 : Webster's Revised Unabridged Dictionary (1913)

Diurnal \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. (Zo["o]l.) 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}.