<p><strong>Noun:</strong></p><ul><li>Geometry: a solid geometric figure generated by the revolution of a semicircle about its diameter; a round body whose surface is at all points equidistant from the center.</li><li>the surface of such a figure; a spherical surface.</li><li>any rounded body approximately of this form; a globular mass, shell, etc.</li><li>Astronomy: a planet or star; heavenly body.</li><li>celestial sphere.</li><li>any of the transparent, concentric, spherical shells, or layers, in which, according to ancient belief, the planets, stars, and other heavenly bodies were set.</li><li>the place or environment within which a person or thing exists; a field of activity or operation: to be out of one's professional sphere.</li><li>a particular social world, stratum of society, or walk of life: His social sphere is small.</li><li>a field of something specified: a sphere of knowledge.</li></ul>