noun
- plural of directrix; fixed lines used as references in defining conic sections such as parabolas, ellipses, and hyperbolas
Usage: mathematics; geometry
Examples
- The parabola is defined by its focus and directrix.
- In geometry class, we learned how directrices help construct conic sections.
- The ellipse has two foci and two directrices.
- Each branch of the hyperbola corresponds to a different directrix.
- The distance ratio from any point on the curve to the focus and directrix remains constant.