Definition:Concyclic Points

Definition
A set of points $S = \left\{{P_1, P_2, \ldots, P_n}\right\}$ is concyclic if they all lie on the circumference of a circle.


 * Concyclic.png

In the above diagram, points $B, C, D, E$ are concyclic, as they all lie on the circumference of the circle centered at $A$.