What is the shortest route between any two points on a sphere called?

The shortest route between any two points on a sphere is known as the Great Circle Route. This concept is based on the geometry of a sphere, where the Great Circle represents the intersection of the sphere with a plane that passes through the center of the sphere.

When traveling over the surface of the Earth, which is roughly spherical, the Great Circle Route is the most efficient path in terms of distance. This is why airliners often follow Great Circle paths in their flight plans, as it allows them to minimize fuel consumption and travel time.

The other terms listed represent different types of navigation or routes. A straight line would imply a linear path on a flat surface rather than on a curved sphere. A Rhumb Line, while useful for navigation, represents a path of constant compass direction, which is not necessarily the shortest route. A Chord Line refers to the straight line segment connecting two points through the interior of a sphere, but it does not account for the curvature of the surface. Thus, the Great Circle Route is distinct in its significance as the shortest path on a curved surface, such as the Earth.