GREAT CIRCLE. The circle in which a Sphere is cut by a plane is called a " great circle," when the cutting plane passes through the centre of Sphere. Treating the earth as a Sphere, the meridians of longitude are all great circles. Of the parallels of latitude, the equator only is a great circle. The shortest line joining any two points is an arc of a great circle. For " great circle sailing " see NAVIGATION.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)