ETYM Old Eng. spere, Old Fren. espere, French sphčre, Latin sphaera. Greek spheros a sphere, a ball.
1. A three-dimensional closed surface such that every point on the surface is equidistant from the center.
2. Any ball-shaped artifact.
3. A solid figure bounded by a spherical surface (including the space it encloses).
4. A particular environment or walk of life; SYN. domain, area, orbit, field, arena.
5. The geographical area in which one nation is very influential; SYN. sphere of influence.
In mathematics, a perfectly round object with all points on its surface the same distance from the center. This distance is the radius of the sphere. For a sphere of radius r, the volume V = 4/3pr3 and the surface area A = 4pr2.