hemisphere: Half of a globe is called a hemisphere. Each half is called a hemisphere. The prefix "hemi" comes from the ancient Greek word for "half." A planet or moon is divided in half by its equator (an imaginary circle). The northern hemisphere is the half between the imaginary circle and the geographic North Pole. The southern hemisphere is the half between the imaginary circle and the geographic South Pole. A globe can also be divided in half by an imaginary circle through the North and South poles creating eastern and western hemispheres.
