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any continuous area that differs in some respect, or is distinguished for some purpose, from adjoining areas, or within which certain distinctive circumstances exist or are established: The temperature lies outside the danger zone.

Geography.��any of five great divisions of the earth's surface, bounded by lines parallel to the equator and named according to the prevailing temperature.

Biogeography.��an area characterized by a particular set of organisms, whose presence is determined by environmental conditions, as an altitudinal belt on a mountain.

Geology.��a horizon.

Geometry.��a part of the surface of a sphere included between two parallel planes.

a specific district, area, etc., within which a uniform charge is made for transportation, mail delivery, or other service.

the total number of available railroad terminals within a given circumference around a given shipping center.

an area or district in a city or town under special restrictions as to the type, size, purpose, etc., of existing or proposed buildings.

time zone.

Also called postal delivery zone.��(in the U.S. postal system) any of the numbered districts into which a city or metropolitan area was formerly divided for expediting the sorting and delivery of mail.

Sports.��a particular portion of a playing area.

Informal.��the zone, a state of intense concentration and focus that greatly improves a person's performance in a physical or mental activity, especially in sports.

Archaic.��a girdle or belt; cincture.

to mark with zones or bands.

to divide into zones, tracts, areas, etc., as according to existing characteristics or as distinguished for some purpose.

to divide (a city, town, neighborhood, etc.) into areas subject to special restrictions on any existing or proposed buildings.

to encircle or surround with a zone, girdle, belt, or the like.