Cyclic
From AoPSWiki
This article is a stub. Help us out by expanding it.
A polygon is cyclic if it can be inscribed in a circle. All triangles and all regular polygons are cyclic. In a cyclic polygon, the circle in which it can be inscribed is called its circumcircle. The radius of this circle is known as the circumradius of the polygon.
Because two different circles intersect in at most two points, any polygon can be inscribed in at most one circle.
