Quadric surfaces

A quadric surface is a subvariety of P2 defined by the vanishing of a degree 2 homogeneous polynomial.

Special cases

 * Smooth quadric surface
 * Quadric cone
 * Union of two planes in P3
 * Doubled plane in P3

Generalizations

 * Surfaces in P3
 * Quadric hypersurfaces
 * Segre embeddings