The Western Hemisphere, also Western hemisphere or western hemisphere, is a geographical term for the half of the Earth that lies west of the Prime Meridian (which crosses Greenwich, London, United Kingdom), the other half being the eastern hemisphere. It is also used, mainly in North America, to specifically refer to the Americas (or the New World) and adjacent waters, while excluding other territories that lie geographically in Western Hemisphere (parts of Africa, Europe, Antarctica, and Asia); thus, it is sometimes referred to as the American hemisphere.
Any definition of eastern and western hemispheres, however, requires the selection of an arbitrary meridian and a corresponding meridian on the other side of the Earth. The Prime Meridian at 0° longitude is typically used, which runs through Greenwich; this is used to define the International Date Line (or End Meridian) on the other side of the Earth at 180° longitude. In its proper geographic sense, the western hemisphere includes not only the Americas, but the western portions of Europe and Africa, the easternmost tip of Russia, numerous territories in Oceania, and a portion of Antarctica while excluding some of the Aleutian Islands to the southwest of the Alaskan mainland. Sometimes, the meridians of 20° W and the diametrically opposed 160° E are used, which excludes the European and African mainlands but also excludes a small portion of northeast Greenland and includes more of eastern Russia and Oceania (e.g., New Zealand).
The two major regions of Antarctica are named after their positions mainly within a single hemisphere; West Antarctica is named for the Western Hemisphere.
Countries common to both hemispheres
Below is a list of the countries which are in both the Western and Eastern hemispheres on the Prime Meridian, in order from north to south:
Below is a list of the countries which are in both the Western and Eastern hemispheres along the 180th meridian, in order from north to south:
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