(geometry) An imaginary line around which an object spins (an axis of rotation) or is symmetrically arranged (an axis of symmetry).

The alliance (in effect before and during World War II) of Germany, Italy, Japan, and several minor allied countries, which opposed the Allies.

An imaginary line through the center of an object, around which it turns.

Relating to the axis

The optical axis. / (crystallography, mineralogy) The direction in which a ray of light passing through a crystal does not suffer double refraction.

The spin axis of a freely rotating body. In the case of the Earth, it differs from the figure axis by a few meters. This difference being a partial cause of the Earth's wobble.

The symmetrical axis of a body. In the case of the Earth, it differs from the rotational axis by a few meters, and so is a partial cause of the Earth's wobble.

The shortest diameter of an ellipse, which bisects the major axis at a right angle.

The brain and the spinal cord

(anatomy) Synonym of cerebrospinal axis