An axis is a real or imaginary straight line around which something rotates or is symmetrically arranged.

Picture a globe spinning on its stand. That rod running through the middle from the North Pole to the South Pole? That's representing Earth's axis, the invisible line our planet spins around once every 24 hours, giving us day and night. A spinning top rotates on its axis too, wobbling and turning around that central line.

In mathematics, an axis is one of the reference lines used to locate points on a graph. The horizontal line is called the x-axis, and the vertical line is the y-axis. When you plot a point like (3, 5), you're measuring three units along the x-axis and five units up the y-axis. These axes work like the grid lines on a map, helping you describe exactly where something is located.

The word can also describe a line of symmetry. If you fold a butterfly drawing down its middle, that center line is an axis of symmetry: both halves mirror each other perfectly. Many shapes, from rectangles to circles, have one or more axes of symmetry.

In World War II, the Axis powers were Germany, Italy, and Japan, who formed an alliance.