A sphere is defined as a three-dimensional closed surface where every point is equidistant from the center point, or the solid figure bounded by this surface. The equation for a sphere is (x–a)2 + (y–b)2 + (z–c)2 = r2, where (a, b, c) are the coordinates of the center and r is the radius. The surface area of a sphere is 4πr2 and the volume is 4πr3/3.

1. Define of sphere :
a. a three-dimensional closed surface such that every point on the
surface is equidistant from a given point, the centre
b. the solid figure bounded by this surface or the space enclosed by it.
Equation: (x–a)2 + (y–b)2 + (z–c)2 = r2, where r is the radius and (a, b, c)
are the coordinates of the centre; surface area: 4πr2; volume: 4πr3/3