Definition:Great Circle/Pole

Definition
Let $S$ be a sphere whose ceneter is $O$.

Let $C$ be a great circle of $S$.

Let $AB$ be the diameter of $S$ situated perpendicular to the plane of $C$.


 * Poles-of-Great-Circle.png

The points $A$ and $B$, where the diameter intersects $S$, are the poles of the great circle $C$.