directrix

[ dih-rek-triks, dahy- ]

/ dɪˈrɛk trɪks, daɪ- /

noun, plural di·rec·trix·es, di·rec·tri·ces [dih-rek-tri-seez, dahy-, dahy-rek-trahy-seez] /dɪˈrɛk trɪˌsiz, daɪ-, ˌdaɪ rɛkˈtraɪ siz/.

Geometry. a fixed line used in the description of a curve or surface.

Archaic. a directress.

Nearby words

directorial, directorship, directory, directory assistance, directress, directrix, diredawa, direful, direfully, direly, diremption

Origin of directrix

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

Usage note

See -trix.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for directrix

The surface formed by revolving the catenary about its directrix is named the alysseide.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5|Various
If a parabola roll on another parabola, their vertices coinciding, the focus of the first traces out the directrix of the second.
The Romance of Mathematics|P. Hampson
The centre of a circle is its focus, and its directrix has gone to infinity, having no special direction.
Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6|Various
Similarly, in an hyperbola a vertex is nearer 704 to the directrix than to the focus.
Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6|Various

If the directrix, focus and eccentricity be given, we may employ the general method for constructing a conic.
Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3|Various

British Dictionary definitions for directrix

directrix

/ (dɪˈrɛktrɪks, daɪ-) /

noun

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

a directress

Word Origin for directrix

C17: New Latin, feminine of director

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for directrix

directrix

[ dĭ-rĕk′trĭks ]

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