directrix

[ dih-rek-triks, dahy- ]

noun

, plural di·rec·trix·es, di·rec·tri·ces [dih-, rek, -tri-seez, dahy-, dahy-rek-, trahy, -seez].

1. Geometry. a fixed line used in the description of a curve or surface.
2. Archaic. a directress.

directrix

/ daɪ-; dɪˈrɛktrɪks /

noun

1. geometry a fixed reference line, situated on the convex side of a conic section, that is used when defining or calculating its eccentricity
2. a directress

directrix

/ dĭ-rĕk′trĭks /

1. A straight line used in generating a curve such as a parabola.

Gender Note

See -trix.

Word History and Origins

Origin of directrix¹

From New Latin, dating back to 1615–25; direct, -trix

Word History and Origins

Origin of directrix¹

C17: New Latin, feminine of director

Example Sentences

The populace went unimpeded about their business, little regarding the detonations, betraying no notice that invisible to sight, all about us on the streets and the green sward of the hillside were extended sweeping the dotted lines of ordnance calculation and the hovering directrix, focus, and vector of martial geometry.

From Literature

Supply dates and a budget and just let the Cruise Directrix take over, since it’s the obstacles that upset her, apparently, and not the planning itself.

From Washington Post

In addition to the archeus, which he described as “aura vitalis seminum, vitae directrix,” Van Helmont had other governing agencies resembling the archeus and not always clearly distinguished from it.

From Project Gutenberg

The “axis” of a circular cylinder is the line joining the centres of two circular sections; it is the line through the centre of the directrix parallel to the generators.

From Project Gutenberg

A cylindrical surface, or briefly a cylinder, is the surface traced out by a line, named the generatrix, which moves parallel to itself and always passes through the circumference of a curve, named the directrix; the name cylinder is also given to the solid contained between such a surface and two parallel planes which intersect a generatrix.

From Project Gutenberg