# Meaning of directrix in English:

## directrix

### nounplural noun directrices/dɪˈrɛktrɪsiːz/ /dʌɪˈrɛktrɪsiːz/

Geometry
• A fixed line used in describing a curve or surface.

‘In the following, the feet of perpendiculars dropped from points A, B, etc. on the parabola to the directrix will be denoted A ’, B ’, etc.’
• ‘The focus and directrix of a hyperbola were considered by Pappus.’
• ‘The directrix is used in the construction, which follows, mutatis mutandis, the same course as the above construction in the case of the ellipse.’
• ‘It is the pedal curve of the parabola where the pedal-point is taken as the reflection of the focus in the directrix.’
• ‘The hyperboloid is then indented and connected to a series of hyperbolic paraboloids through their common directrices, thereby leading the ensemble toward the four load-bearing points to the ground.’

## directrix

/dɪˈrɛktrɪks/ /dʌɪˈrɛktrɪks/

### Origin

Early 18th century from medieval Latin, literally ‘directress’, based on Latin dirigere ‘to guide’.