- Of or relating to geometric surfaces that are defined by quadratic equations.
- In <em>algebra</em>, a homogeneous expression of the second degree in the variables.
- In <em>algebra</em> and <em>geometry</em>, of the second degree; quadratic.
- Of or pertaining to the second degree.
- A quantic of the second degree. See <xref urlencoded="quantic">quantic</xref>.
- A surface whose equation in three variables is of the second degree. Spheres, spheroids, ellipsoids, paraboloids, hyperboloids, also cones and cylinders with circular bases, are quadrics.
- A <xref>surface</xref> whose shape is defined in terms of a <xref>quadratic equation</xref>
- a curve or surface whose equation (in Cartesian coordinates) is of the second degree