directrix

di·rec·trix

noun \-ˈrek-triks\

plural di·rec·trix·es\-trik-səz\ also di·rec·tri·ces\-trə-ˌsēz\

Definition of DIRECTRIX

1

archaic : directress

2

: a fixed curve with which a generatrix maintains a given relationship in generating a geometric figure; specifically : a straight line the distance to which from any point of a conic section is in fixed ratio to the distance from the same point to a focus

Origin of DIRECTRIX

Medieval Latin, feminine of Late Latin director, from Latin dirigere

First Known Use: 1622