Ab·er·ra·tion n.
 1. The act of wandering; deviation, especially from truth or moral rectitude, from the natural state, or from a type.   “The aberration of youth.” --Hall. “Aberrations from theory.” --Burke.
 2. A partial alienation of reason.  “Occasional aberrations of intellect.” --Lingard.
    Whims, which at first are the aberrations of a single brain, pass with heat into epidemic form.   --I. Taylor.
 3. Astron. A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer; called annual aberration, when the observer's motion is that of the earth in its orbit, and daily or diurnal aberration, when of the earth on its axis; amounting when greatest, in the former case, to 20.4'', and in the latter, to 0.3''. Planetary aberration is that due to the motion of light and the motion of the planet relative to the earth.
 4. Opt. The convergence to different foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus; called spherical aberration, when due to the spherical form of the lens or mirror, such form giving different foci for central and marginal rays; and chromatic aberration, when due to different refrangibilities of the colored rays of the spectrum, those of each color having a distinct focus.
 5. Physiol. The passage of blood or other fluid into parts not appropriate for it.
 6. Law The producing of an unintended effect by the glancing of an instrument, as when a shot intended for A glances and strikes B.
 Syn: -- Insanity; lunacy; madness; derangement; alienation; mania; dementia; hallucination; illusion; delusion. See Insanity.

 ◄ ►


 Di·ur·nal a.
 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. Zool. 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.