(mathematics) A regular three-dimensional object in which every cross-section is a circle; the figure described by the revolution of a circle about its diameter .

A spherical physical object; a globe or ball.

(astronomy, now rare) The celestial sphere: the edge of the heavens, imagined as a hollow globe within which celestial bodies appear to be embedded.

(historical, astronomy, mythology) 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).

(mythology) An area of activity for a planet; or by extension, an area of influence for a god, hero etc.

(figurative) The region in which something or someone is active; one's province, domain.

The natural, normal, or proper place (of something).

(geometry) The set of all points in three-dimensional Euclidean space (or n-dimensional space, in topology) that are a fixed distance from a fixed point .

(transitive) To place in a sphere, or among the spheres; to ensphere.

(transitive) To make round or spherical; to perfect.