noun A surface in three dimensions consisting of all points equidistant from a center. .mw-parser-output .defdate{font-size:smaller}.
noun An object which appears to be bounded by a sphere; a round object, a ball.
noun The celestial sphere: the edge of the heavens, imagined as a hollow globe within which celestial bodies appear to be embedded.
noun 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).
noun An area of activity for a planet; or by extension, an area of influence for a god, hero etc.
noun The region in which something or someone is active; one's province, domain.
sphere of influence
noun The natural, normal, or proper place (of something).
in one's sphere
noun 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 .