directrix
Americannoun
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directrixes,
plural
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directrices
plural
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Geometry. a fixed line used in the description of a curve or surface.
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Archaic. a directress.
noun
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geometry a fixed reference line, situated on the convex side of a conic section, that is used when defining or calculating its eccentricity
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a directress
Gender
See -trix.
Other Word Forms
Noun Inflected Forms
Etymology
Origin of directrix
From New Latin, dating back to 1615–25; see origin at direct, -trix
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Hyperbola with and directrix units above the pole.
From Textbooks ● Dec. 21, 2021
Ellipse with and directrix unit above the pole.
From Textbooks ● Dec. 21, 2021
The fixed point is called the focus, and the fixed line is called the directrix of the parabola.
From Textbooks ● May 6, 2020
Notice that the axis of symmetry passes through the focus and vertex and is perpendicular to the directrix.
From Textbooks ● Feb. 13, 2015
With your permission I will add a few words to those I have already uttered with regard to the directrix.
Figure 7.54 The three conic sections with their foci and directrices.
From Textbooks ● Mar. 30, 2016
Figure 1.54 The three conic sections with their foci and directrices.
From Textbooks ● Mar. 30, 2016
The surface may be considered as generated by an ellipse moving parallel to itself along two ellipses as directrices.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various
In the ellipse, which lies between the directrices, d1 + d2 is constant, therefore also r1 + r2.
From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various
The ellipse and the hyperbola have two foci and two directrices.
From An Elementary Course in Synthetic Projective Geometry by Derrick Norman Lehmer
The ellipse and hyperbola have each two foci, and two corresponding directrixes, and the parabola has one focus and one directrix.
From The Gutenberg Webster's Unabridged Dictionary Section F, G and H by Project Gutenberg
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