5. Rotation: Rotation is the movement of the earth on its axis.

Revolution: The movement of the earth around the sun in a fixed path or orbit is called revolution.

Orbital Plane: The plane formed by the orbit is known as orbital plane.

Circle of illumination: The portion facing the sun experiences day while the other half away from the sun experiences night. The circle that divides the day from night on the globe is called the circle of illumination.

Leap year: A year with 366 days is called a leap year.

Equinox: On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.