资料来源 : Webster's Revised Unabridged Dictionary (1913)

Latus rectum \La"tus rec"tum\ [L., the right side.] (Conic
   Sections)
   The line drawn through a focus of a conic section parallel to
   the directrix and terminated both ways by the curve. It is
   the parameter of the principal axis. See {Focus}, and
   {Parameter}.