directrix

[ dih-rek-triks, dahy- ]

/ dɪˈrɛk trɪks, daɪ- /

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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.

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Origin of directrix

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

usage note for directrix

See -trix.

Words nearby directrix

direct primary, direct product, direct question, direct-reading, directress, directrix, direct selling, direct speech, direct sum, direct tax, direct-vision prism

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use directrix in a sentence

The surface formed by revolving the catenary about its directrix is named the alysseide.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5|Various
Since the tension is measured by the height above the directrix these two catenaries have the same directrix.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3|Various
The only surface of revolution having this property is the catenoid formed by the revolution of a catenary about its directrix.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3|Various
Hence T, the point of intersection of Pp and Qq, must be the centre of similitude and must be on the common directrix.
Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3|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

Scientific definitions for directrix

directrix

[ dĭ-rĕk′trĭks ]

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