the line about which a rotating body, such as the earth, turns.
2.
Mathematics.
a.
a central line that bisects a two-dimensional body or figure.
b.
a line about which a three-dimensional body or figure is symmetrical.
3.
Anatomy.
a.
a central or principal structure, about which something turns or is arranged: the skeletal axis.
b.
the second cervical vertebra.
4.
Botany. the longitudinal support on which organs or parts are arranged; the stem and root; the central line of any body.
5.
Analytic Geometry. any line used as a fixed reference in conjunction with one or more other references for determining the position of a point or of a series of points forming a curve or a surface. Compare x-axis, y-axis.
Aeronautics. any one of three lines defining the attitude of an airplane, one being generally determined by the direction of forward motion and the other two at right angles to it and to each other.
8.
Fine Arts. an imaginary line, in a given formal structure, about which a form, area, or plane is organized.
9.
an alliance of two or more nations to coordinate their foreign and military policies, and to draw in with them a group of dependent or supporting powers.
10.
the Axis, (in World War II) Germany, Italy, and Japan, often with Bulgaria, Hungary, and Romania.
11.
a principal line of development, movement, direction, etc.
[Origin: 1540–50; < L axis an axletree, axle, axis. See axi-]
A straight line about which a body or geometric object rotates or may be conceived to rotate.
Mathematics
An unlimited line, half-line, or line segment serving to orient a space or a geometric object, especially a line about which the object is symmetric.
A reference line from which distances or angles are measured in a coordinate system.
The second cervical vertebra on which the head turns.
Any of various central structures, such as the spinal column, or standard abstract lines used as a positional referent.
An alliance of powers, such as nations, to promote mutual interests and policies.
Axis The alliance of Germany and Italy in 1936, later including Japan and other nations, that opposed the Allies in World War II.
A center line to which parts of a structure or body may be referred.
An imaginary line to which elements of a work of art, such as a picture, are referred for measurement or symmetry.
Anatomy
The second cervical vertebra on which the head turns.
Any of various central structures, such as the spinal column, or standard abstract lines used as a positional referent.
An alliance of powers, such as nations, to promote mutual interests and policies.
Axis The alliance of Germany and Italy in 1936, later including Japan and other nations, that opposed the Allies in World War II.
Botany The main stem or central part about which organs or plant parts such as branches are arranged.
One of three mutually perpendicular lines that define the orientation of an aircraft, with one being along its direction of travel and the other two being perpendicular to the direction of travel.
A line through the optical center of a lens that is perpendicular to both its surfaces.
One of three or four imaginary lines used to define the faces of a crystal and the position of its atoms.
An alliance of powers, such as nations, to promote mutual interests and policies.
Axis The alliance of Germany and Italy in 1936, later including Japan and other nations, that opposed the Allies in World War II.
1549, "imaginary straight line around which a body (such as the Earth) rotates," from L. axis "axle, pivot, axis of the earth or sky," from PIE *aks- "axis" (cf. O.E. eax, O.H.G. ahsa "axle," Gk. axon, Skt. aksah "an axle, axis, beam of a balance," Lith. aszis). Fig. sense in world history of "alliance between Germany and Italy" (later extended to include Japan) is from 1936.
An imaginary line around which an object rotates. In a rotating sphere, such as the Earth and other planets, the two ends of the axis are called poles. The 23.45° tilt of the Earth's axis with respect to the plane of its orbit around the Sun causes the Northern and Southern Hemispheres to point toward and away from the Sun at different times of the year, creating seasonal patterns of weather and climate. Other planets in the solar system have widely varying tilts to their axes, ranging from near 0° for Mercury to 177° for Venus.
Mathematics
A line, ray, or line segment with respect to which a figure or object is symmetrical.
A reference line from which distances or angles are measured in a coordinate system, such as the x-axis and y-axis in the Cartesian coordinate system.
Anatomy The second cervical vertebra, which serves as a pivot for the head.
Botany The main stem or central part of a plant or plant part, about which other plant parts, such as branches or leaflets, are arranged.
Ax"is\, n.; pl. Axes. [L. axis axis, axle. See Axle.] A straight line, real or imaginary, passing through a body, on which it revolves, or may be supposed to revolve; a line passing through a body or system around which the parts are symmetrically arranged. 2. (Math.) A straight line with respect to which the different parts of a magnitude are symmetrically arranged; as, the axis of a cylinder, i. e., the axis of a cone, that is, the straight line joining the vertex and the center of the base; the axis of a circle, any straight line passing through the center. 3. (Bot.) The stem; the central part, or longitudinal support, on which organs or parts are arranged; the central line of any body. --Gray. 4. (Anat.) (a) The second vertebra of the neck, or vertebra dentata. (b) Also used of the body only of the vertebra, which is prolonged anteriorly within the foramen of the first vertebra or atlas, so as to form the odontoid process or peg which serves as a pivot for the atlas and head to turn upon. 5. (Crystallog.) One of several imaginary lines, assumed in describing the position of the planes by which a crystal is bounded. 6. (Fine Arts) The primary or secondary central line of any design. Anticlinal axis (Geol.), a line or ridge from which the strata slope downward on the two opposite sides. Synclinal axis, a line from which the strata slope upward in opposite directions, so as to form a valley. Axis cylinder (Anat.), the neuraxis or essential, central substance of a nerve fiber; -- called also axis band, axial fiber, and cylinder axis. Axis in peritrochio, the wheel and axle, one of the mechanical powers. Axis of a curve (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. Axis of a lens, the straight line passing through its center and perpendicular to its surfaces. Axis of atelescope or microscope, the straight line with which coincide the axes of the several lenses which compose it. Axes of co["o]rdinates in a plane, two straight lines intersecting each other, to which points are referred for the purpose of determining their relative position: they are either rectangular or oblique. Axes of co["o]rdinates in space, the three straight lines in which the co["o]rdinate planes intersect each other. Axis of a balance, that line about which it turns. Axis of oscillation, of a pendulum, a right line passing through the center about which it vibrates, and perpendicular to the plane of vibration. Axis of polarization, the central line around which the prismatic rings or curves are arranged. --Brewster. Axis of revolution (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. Axis of symmetry (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. Axis of theequator, ecliptic, horizon (or other circle considered with reference to the sphere on which it lies), the diameter of the sphere which is perpendicular to the plane of the circle. --Hutton. Axis of the Ionic capital (Arch.), a line passing perpendicularly through the middle of the eye of the volute. Neutral axis (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. Optic axis of a crystal, 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. Optic axis, Visual axis (Opt.), the straight line passing through the center of the pupil, and perpendicular to the surface of the eye. Radical axis of two circles (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. Spiral axis (Arch.), the axis of a twisted column drawn spirally in order to trace the circumvolutions without. Axis of abscissas and Axis of ordinates. See Abscissa.
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