Axis has several uses.
In mathematics, an axis is a straight line around which a geometric figure can be rotated. An axis of symmetry is a line with respect to which a body can be symmetrical. The term is also applied for the axis of a graph; the horizontal axis x-axis, the vertical y-axis and the z-axis is a possible third axis used for three-dimensional graphing.
In anatomy, the axis (C2) is the second cervical vertebra of the spine. Its articulation with the bone above, the atlas, allows rotation, and its articulation with the bone below (C3) allows a lesser degree of flexion, tilting and rotation.
In history, Axis can also be used to denote an alliance or partnership. When talking about the Axis (capitalised), usually the alliance of Germany, Italy and Japan in World War II is meant (see Axis Powers). George W. Bush also coined the term Axis of Evil, although the three countries listed (Saddam Hussein's Iraq, Iran, and North Korea) may not have been working together.