geometric hemisphere
In geometry a hemisphere is an exact half of a sphere.
{hemi-prefix : hemi-half. Origin from Greek hēmi; related to Latin semi.}
It also refers to half of the Earth, such as the "Northern Hemisphere" (that part of the Earth north of the equator), or "Western Hemisphere" (the half of the Earth west of a line running from the North Pole
through England to the South Pole, includes the Americas