In mathematics, a paraboloid is a quadric, a type of surface in three dimensions, described by the equation:
or
\left( \frac{x}{a} \right) ^2 + \left( \frac{y}{b} \right) ^2 + 2z = 0
</math> (elliptic paraboloid),
\left( \frac{x}{a} \right) ^2 - \left( \frac{y}{b} \right) ^2 + 2z = 0
</math> (hyperbolic paraboloid).