See Also: directrix(medicine)
directrix(dictionary)

directrix (iou)



directrix noun. . E16.
[medieval Latin, fem. of late Latin DIRECTOR: see -TRIX.]
= DIRECTRESS. E16.
Geometry. A fixed line with reference to which a curve or surface is defined; spec. the straight line the distance of which from any point on a conic bears a constant ratio to the distance of the same point from the focus. E18.