Sphere
Part of speech: noun
Definition: 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). 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.
Example sentence: The pursuit of truth and beauty is a sphere of activity in which we are permitted to remain children all our lives.
Sector
Part of speech: noun
Definition: sectionzoneA part of a circle, extending to the center.a fixed-sized unit (traditionally 512 bytes) of sequential data stored on a track of a digital medium (compare to block)An area designated by boundaries within which a unit operates, and for which it is responsible.One of the subdivisions of a coastal frontier.a fictional region of space designated for navigational or governance purposes; for instance, W:Sector (Star Trek), W:List of Star Wars sectors
Example sentence: There can be no doubt that the transportation sector is the most critical sector of our economy.