AXIS, a straight line, real or imagi nary, passing through a body, and around which that body revolves, or at least may revolve; also, the imaginary line con necting the poles of a planet, and around which the planet rotates.
In geometry, an imaginary line drawn through a plane figure, and about which the plane figure is supposed to revolve, with the result of defining the limits of a solid.
In astronomy the axis of the earth or the axis of rotation of the earth, is that diameter about which it revolves. It is the one which has for its extremities the North and South Poles. The term is similarly used of the sun, the moon, and the planets. The axis of the celestial sphere is the imaginary line around which the heavens appear to revolve. The axis of an orbit is the major axis of the orbit of a planet, the lino joining the aphelion and perihelion points. The minor axis is the line perpendicular to the former, and passing through the center of the ellipse.
In mechanics, the axis of suspension of a pendulum is the point from which it is suspended, and, consequently, around which it turns.
In optics, the axis of a lens is a line passing through the center of its curved, and perpendicular to its plane, surface.
In architecture, a spiral axis is the axis of a spirally twisted column. The axis of an Ionic capital is a line passing perpendicularly through the middle of the eye of the volute.
In geology an axis is an imaginary line on the opposite sides of which the strata dip in different directions. If the angle formed at their point of junction be a salient one, they form an anticlinal axis, or anticlinal; but, if it is a re entering one, then they constitute a synclinal axis, or synclinal.
In botany, the axis is that part of a plant around which the organs are sym metrically arranged. The ascending axis means the stem. The descending axis is the root. Recessory axes are axes in addition to the main one, found in the stems of calycanthus, chimonanthus, and some other plants. The appendages of the axis are scales, leaves, bracts, flowers, sexes, and fruit. The axis of in florescence is a peduncle which proceeds in a nearly straight line from the base to the apex of the inflorescence.
In anatomy, the axis of the body is the vertebral column, around which the other portions of the frame are arranged.