The geometric locus of points that are the same distance from a point called the centre of the sphere.

A sphere may be obtained by rotating a circle about its diameter.

- In the illustration below, the axis
*z*contains a diameter of the circle.

- A sphere does not have a net.
- The diameter of a sphere is the line segment that joins two points of a sphere and that passes through the centre of the sphere.
- A great circle is the intersection of a sphere and a plane passing through the centre of a sphere.
- A small circle is a section of a sphere formed by the intersection of a sphere and a plane that does not pass through the centre of the sphere.

### Formulas

- The area \(A\) of a sphere of radius \(r\) is : \(A=4\pi r^{2}\)
- The volume \(V\) of a sphere of radius \(r\) is : \(V=\dfrac{4\pi r^{3}}{3}\)
- The area of a sphere is equal to \(\dfrac{2}{3}\) of the total area of its circumscribed cylinder.
- The area of a sphere is equal to \(\dfrac{4}{9}\) of the total area of its circumscribed right circular cone.
- The volume of the space bounded by a sphere is equal to \(\dfrac{2}{3}\) of the volume of its circumscribed cylinder.
- The volume of the space bounded by a sphere is equal to \(\dfrac{4}{9}\) of the volume of its circumscribed right circular cone.