The points of the Poincaré universe are the points of the unit disk in the complex plane, i.e. is a point of the Poincaré universe whenever (the yellow points in the sketch). Thus is a point, since , but and are not, since and . We'll call the unit circle the edge circle, or simply the edge, and its points (the red points in the diagram) edgepoints. Edgepoints are not part of the Poincaré universe, but are used to help describe its geometry.