1. The apparent displacement, or difference of position, of an object, as seen from two different stations,
or points of view.
2. (Astron.) The apparent difference in position of a body (as the sun, or a star) as seen from some
point on the earth's surface, and as seen from some other conventional point, as the earth's center or
Annual parallax, the greatest value of the heliocentric parallax, or the greatest annual apparent change
of place of a body as seen from the earth and sun; as, the annual parallax of a fixed star. Binocular
parallax, the apparent difference in position of an object as seen separately by one eye, and then by
the other, the head remaining unmoved. Diurnal, or Geocentric, parallax, the parallax of a body
with reference to the earth's center. This is the kind of parallax that is generally understood when the
term is used without qualification. Heliocentric parallax, the parallax of a body with reference to
the sun, or the angle subtended at the body by lines drawn from it to the earth and sun; as, the heliocentric
parallax of a planet. Horizontal parallax, the geocentric parallx of a heavenly body when in the
horizon, or the angle subtended at the body by the earth's radius. Optical parallax, the apparent
displacement in position undergone by an object when viewed by either eye singly. Brande & C.
Parallax of the cross wires their apparent displacement when the eye changes its position, caused
by their not being exactly in the focus of the object glass. Stellar parallax, the annual parallax of a
(Par"al*lel) a. [F. parallèle, L. parallelus, fr. Gr. para` beside + of one another, fr. other, akin to
L. alius. See Allien.]
1. (Geom.) Extended in the same direction, and in all parts equally distant; as, parallel lines; parallel
Revolutions . . . parallel to the equinoctial.Hakluyt.
Curved lines or curved planes are said to be parallel when they are in all parts equally distant.
2. Having the same direction or tendency; running side by side; being in accordance (with); tending to the
same result; used with to and with.
When honor runs parallel with the laws of God and our country, it can not be too much cherished.Addison.
3. Continuing a resemblance through many particulars; applicable in all essential parts; like; similar; as, a
parallel case; a parallel passage. Addison.
Parallel bar. (a) (Steam Eng.) A rod in a parallel motion which is parallel with the working beam.
(b) One of a pair of bars raised about five feet above the floor or ground, and parallel to each other,
used for gymnastic exercises. Parallel circles of a sphere, those circles of the sphere whose
planes are parallel to each other. Parallel columns, or Parallels (Printing), two or more passages
of reading matter printed side by side, for the purpose of emphasizing the similarity or discrepancy between
them. Parallel forces (Mech.), forces which act in directions parallel to each other. Parallel
motion. (a) (Mach.) A jointed system of links, rods, or bars, by which the motion of a reciprocating
piece, as a piston rod, may be guided, either approximately or exactly in a straight line. Rankine. (b)
(Mus.) The ascending or descending of two or more parts at fixed intervals, as thirds or sixths. Parallel
rod (Locomotive Eng.), a metal rod that connects the crank pins of two or more driving wheels; called
also couping rod, in distinction from the connecting rod. See Illust. of Locomotive, in App. Parallel
ruler, an instrument for drawing parallel lines, so constructed as to have the successive positions of the
ruling edge parallel to each other; also, one consisting of two movable parts, the opposite edges of which
are always parallel. - - Parallel sailing (Naut.), sailing on a parallel of latitude. Parallel sphere
(Astron. & Geog.), that position of the sphere in which the circles of daily motion are parallel to the
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