(optics) An imaginary line within an optical system around which there is rotational symmetry.

(geometry) Either of two axes in a conic section, such that each is parallel to the tangent at the extremity of the other.

A chord progression, I–V–vi–IV, used in Western popular music, common since the 1970s.

(astronomy) The axis of Earth between the celestial poles, important in ancient geocentric coordinate systems.

(algebraic geometry) The axis on a graph of at least three dimensions that is usually drawn vertically and usually shows the range of values of a variable dependent on two other variables or the third independent variable.

(algebraic geometry) The axis on a graph that is usually drawn left to right and usually shows the range of values of an independent variable.

(algebraic geometry) The axis on a graph that is usually drawn from bottom to top and usually shows the range of values of variable dependent on one other variable, or the second of two independent variables.

(geometry) Any of one or more lines about which a geometric figure is symmetric

A group of states accused by George W. Bush of sponsoring terrorism and seeking weapons of mass destruction, originally defined as Iran, Iraq, and North Korea.

plural of Axis power