AX'IS, noun plural axes. [Latin ; Gr.]

1. The straight line, real or imaginary, passing through a body, or which it revolves, or may revolve; as the axis of the earth.

2. In geometry, a straight line in a plain figure, about which it revolves to produce a solid.

3. In conic sections, a right line dividing the section into two equal parts, and cutting all its ordinates at right angles.

4. In mechanics, the axis of a balance is that line about which it moves, or rather turns.

The axis of oscillation is a right line parallel to the horizon passing through the center, about which a pendulum vibrates.

The axis in peritrochio is a wheel concentric with the base of a cylinder, and movable with it about its axis

5. In optics, a particular ray of light from any object which falls perpendicularly on the eye.

6. In architecture, spiral axis is the axis of a twisted column spirally drawn in order to trace the circumvolutions without.

Aris of the Ionic capital is a line passing perpendicularly through the middle of the eye of the volute.

The axis of a vessel is an imaginary line passing through the middle of it, perpendicular to its base, and equally distant from its sides.

In botany, axis is a taper column in the center of some flowers or catkins, about which the other parts are disposed.

In anatomy, axis is the name of the second verteber of the neck; it has a tooth which enters into the first verteber, and this tooth is by some called the axis