Two opposite longitudes form

Longitude is the angular distance of a location on Earth's surface east or west of the Prime Meridian, which is an imaginary line that runs from the North Pole to the South Pole and passes through Greenwich, England. Two opposite longitudes form a Great Circle. A Great Circle is a circle on the surface of a sphere that has the same center as the sphere. It is the largest possible circle that can be drawn on a sphere and divides the sphere into two equal hemispheres. Therefore, the answer is: a Great Circle. Two opposite longitudes form a Great Circle, while the Equator is an imaginary circle that lies at 0 degrees latitude, the International Dateline is an imaginary line that runs roughly from the North Pole to the South Pole and defines the change of calendar days, and the Arctic Circle is an imaginary circle that lies at 66.5 degrees North latitude.