In mathematics, a quadric, or quadric surface, is any D-dimensional hypersurface defined as the locus of zeros of a quadratic polynomial. In coordinates \{x_0, x_1, x_2, \ldots, x_D\}, the general quadric is defined by the algebraic equation http://www.geom.uiuc.edu/docs/reference/CRC-formulas/node61.html, Quadrics in Geometry Formulas and Facts by Silvio Levy, excerpted from 30th Edition of the CRC Standard Mathematical Tables and Formulas (CRC Press).

In mathematics, in the area of projective geometry, a quadric in a projective space is the set of points represented by vectors on which a certain non-trivial quadratic form becomes zero.