(topology, complex analysis) The complex numbers extended with the number ∞; the complex plane (representation of the complex numbers as a Euclidean plane) extended with a single idealised point at infinity and consequently homeomorphic to a sphere in 3-dimensional Euclidean space.

(physics) A volume whose radius is the Debye length, in which there is a sphere of influence, and outside of which charges are electrically screened.

plural of sphere packing

(quantum mechanics) A geometrical representation of the pure state space of a two-level quantum-mechanical system, or qubit.

(astronomy) The region in which a given astronomical body dominates the attraction of satellites.

(of a black hole) A region of around a black hole where photons travel in orbits around the singularity, just beyond the event horizon.

A crystal ball

A fold mirror that is a "sphere", i.e. a spherical mirror

(cosmology) Hubble volume

A small object, often spherical to disc-shaped, found in three-billion-year-old pyrophyllite deposits mined near Ottosdal in South Africa.