line-coördinate

from The Century Dictionary.

• noun One of a set of quantities, commonly three in a plane, or six in space, defining the position of a line.
• noun where x, y, z are the trilinear coördinates of a point in a plane. When these are taken as constant, while u, v, w are variable, the equation restricts a line to passing through that point, and any set of values of u, v, w define a line. The above equation determines the incidence of the point on the line, whether u, v, w or x, y, z, or both, be variable. The precise geometrical significance of the line-coördinates depends upon that of the point-coördinates. The six line-coördinates in space are generally termed ray-coördinates.