n.1. a. An area or a region distinguished from adjacent parts by a distinctive feature or characteristic.
b. A section of an area or territory established for a specific purpose, as a section of a city restricted to a particular type of building, enterprise, or activity: a residential zone.
c. An area of a given radius within which a uniform rate is charged, as for transportation or shipping.
2. a. Any of the five regions of the surface of the earth that are loosely divided according to prevailing climate and latitude, including the tropics, the North and South Temperate Zones, and the North and South Polar Regions.
b. A similar division on any other planet.
c. Mathematics A portion of a sphere bounded by the intersections of two parallel planes with the sphere.
3. Ecology An area characterized by distinct physical conditions and supporting a particular type of flora and fauna.
4. Anatomy A ringlike or cylindrical growth or structure.
5. Geology A region or stratum distinguished by composition or content.
6. Sports A zone defense.
7. Archaic A belt or girdle.