Noun
1. a particular environment or walk of life;
"his social sphere is limited""it was a closed area of employment""he's out of my orbit"2. any spherically shaped artifact
3. the geographical area in which one nation is very influential
4. a particular aspect of life or activity;
"he was helpless in an important sector of his life"5. a solid figure bounded by a spherical surface (including the space it encloses)
6. a three-dimensional closed surface such that every point on the surface is equidistant from the center
7. the apparent surface of the imaginary sphere on which celestial bodies appear to be projected