axis : Idioms & Phrases

• (Geol.), a line or ridge from which the strata slope downward on the two opposite sides.

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• (Geol.), a line from which strata dip in opposite directions, as from the ridge of a roof.

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• to straight lines intersecting each other, to which points are referred for the purpose of determining their relative position: they are either rectangular or oblique.

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• the three straight lines in which the coördinate planes intersect each other.

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• (Anat.), the neuraxis or essential, central substance of a nerve fiber; called also axis band, axial fiber, and cylinder axis.

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• the wheel and axle, one of the mechanical powers.

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• that line about which it turns.

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• (Geom.), a straight line which bisects a system of parallel chords of a curve; called a principal axis, when cutting them at right angles, in which case it divides the curve into two symmetrical portions, as in the parabola, which has one such axis, the ellipse, which has two, or the circle, which has an infinite number. The two axes of the ellipse are the major axis and the minor axis, and the two axes of the hyperbola are the transverse axis and the conjugate axis.

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• the straight line passing through its center and perpendicular to its surfaces.

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• the straight line with which coincide the axes of the several lenses which compose it.

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• and

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• . See Abscissa.

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• of a pendulum, a right line passing through the center about which it vibrates, and perpendicular to the plane of vibration.

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• the central line around which the prismatic rings or curves are arranged. Brewster.

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• (Descriptive Geom.), a straight line about which some line or plane is revolved, so that the several points of the line or plane shall describe circles with their centers in the fixed line, and their planes perpendicular to it, the line describing a surface of revolution, and the plane a solid of revolution.

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• noun the center around which something rotates
  axis.
  

WordNet

• (Geom.), any line in a plane figure which divides the figure into two such parts that one part, when folded over along the axis, shall coincide with the other part.

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• the diameter of the sphere which is perpendicular to the plane of the circle. Hutton.

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• (Arch.), a line passing perpendicularly through the middle of the eye of the volute.

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• noun the 2nd cervical vertebra; serves as a pivot for turning the head
  axis.
  

WordNet

• the shorter lateral axis of an orthorhombic crystal.

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• (Math.), the line through the center of the curve, perpendicular to the line through the two foci.

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• noun one of the fixed reference lines of a coordinate system
  

WordNet

• . (Anat.) SeeAxis cylinder, under Axis.

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• (Kinematics), in a body which has motions both of translation and rotation, is a line, which is supposed to be rigidly united with the body, and which for the instant is at rest. The motion of the body is for the instant simply that of rotation about the instantaneous axis.

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• noun the longest axis of an ellipse or ellipsoid; passes through the two foci
  

WordNet

• (Geom.), the greater axis. See Focus, n., 2.

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• noun the shorter or shortest axis of an ellipse or ellipsoid
  

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• (Mech.), the line of demarcation between the horizontal elastic forces of tension and compression, exerted by the fibers in any cross section of a girder.

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• (Mech.), that line or plane, in a beam under transverse pressure, at which the fibers are neither stretched nor compressed, or where the longitudinal stress is zero. See Axis.

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• noun a reflecting telescope with the mirror slightly tilted to throw the image to the side where it can be viewed
  Herschelian telescope.
  

WordNet

• noun in a doubly refracting crystal, the line in the direction of which no double refraction occurs
  
  • a crystal may have either one or two optic axes
• noun a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted
  optic axis.
  
  • in a normal eye the optic axis is the direction in which objects are seen most distinctly

WordNet

• . (Opt.) (a) A line drawn through the center of the eye perpendicular to its anterior and posterior surfaces. In a normal eye it is in the direction of the optic axis that objects are most distinctly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial crystal has one such line, a biaxial crystal has two.

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• (Opt.), the straight line passing through the center of the pupil, and perpendicular to the surface of the eye.

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• the direction in which a ray of transmitted light suffers no double refraction. All crystals, not of the isometric system, are either uniaxial or biaxial.

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• that axis of an astronomical instrument, as an equatorial, which is parallel to the earths axis.

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• (Bot.), the main stalk which bears a whole cluster of flowers.

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• noun a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted
  optic axis.
  
  • in a normal eye the optic axis is the direction in which objects are seen most distinctly

WordNet

• . See Axis of a curve, under Axis.

Webster 1913

• (Geom.), the straight line perpendicular to the line joining their centers and such that the tangents from any point of it to the two circles shall be equal to each other.

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• (Opt.), any line which passes through the optical center of a lens but not through the centers of curvature, or, in the case of a mirror, which passes through the center of curvature but not through the center of the mirror.

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• noun one-half the major axis of an ellipse; the distance from the center of an ellipse to one end
  

WordNet

• noun one-half the minor axis of an ellipse
  

WordNet

• (Arch.), the axis of a twisted column drawn spirally in order to trace the circumvolutions without.

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• a line from which the strata slope upward in opposite directions, so as to form a valley.

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• (of an ellipse or hyperbola) (Geom.), that axis which passes through the foci.

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• . See the Note under Twin, n.

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• noun the horizontal axis in a plane coordinate system
  

WordNet

• noun the vertical axis in a plane coordinate system
  

WordNet

• noun the third axis in a 3-dimensional coordinate system
  

WordNet

• (Crystallog.), a straight line passing through the center of a crystal, to which all the planes of a given zone are parallel.

Webster 1913