Sphere definition

From , from late , earlier , from , of unknown origin.

A regular three-dimensional object in which every cross-section is a circle; the figure described by the revolution of a semi-circle about its diameter.
The set of all points in three-dimensional Euclidean space (or -dimensional space, in topology) that are a fixed distance from a fixed point.
A spherical object; a globe or ball.
The apparent outer limit of space, the edge of the heavens, imagined as a hollow globe within which celestial bodies appear to be embedded.
Any of the concentric hollow transparent globes formerly believed to rotate around the Earth, and which carried the heavenly bodies; there were originally believed to be eight, and later nine and ten; friction between them was thought to cause a harmonious sound (the music of the spheres).
- 1603, John Florio, translating Michel de Montaigne, Essays, vol. 1 p. 153:
  
  It is more simplicitie to teach our children [...] [t]he knowledge of the starres, and the motion of the eighth spheare, before their owne.
An area of activity for a planet; or by extension, an area of influence for a god, hero etc.
The region in which something or someone is active; one's province, domain.

(object): ball, globe, orb
(region of activity): area, domain, field, orbit, sector
(in geometry): 3-sphere (geometry), 2-sphere (topology)
(astronomy: apparent surface of the heavens): See celestial sphere
(astronomy: anything visible on the apparent surface of the heavens): See celestial body