The axis, as a polysemic concept, can have different meanings, referring to the body, generally cylindrical in shape, which crosses another body, of greater dimension, to serve as a center so that it can specify its rotating movements, in addition to the straight lines surrounding the which new figures or surfaces can be generated. Generally, axes are used in geometry; an example of these are the axes of symmetry, a series of lines used to properly divide a figure, making sure, if each is equidistant, that it is completely symmetrical. In mathematics, the axes are used in Cartesian coordinates, in which the functions and equations of analytic geometry are represented.

The terrestrial axis, also called the axis of the poles, is the one on which the Earth constantly rotates; this determines, in the same way, the position of the poles, this being the north (at the upper end) and the south pole (at the lower end), areas or surfaces that coincide perfectly with the central axis of the planet. The axes of rotation, on the other hand, are those imaginary lines from which a rotary movement can be denoted, whose main characteristic is to remain fixed; the best known axis of rotation is that of the earth.

Within anatomical studies, the second cervical vertebra, also known as C2, is called the “axis” or “axis” (the Latin word for axis); this bone can be found above C3 and below the atlas, the one that articulates with the occipital bone. In mechanics, the axes are small pieces that are included together in the center of rotating bodies, serving as a center so that their movement can take place.