LOCUS GEOMETRICUS, denotes a line by which a
local or indeterminate problem is solved.
A locus is a line, any point of which may equally
solve an indeterminate problem. Thus if a right line
suffice for the construction of the equation, it is called
locus ad rectum; if a circle, locus ad circumulum; if a pa-
rabela, locus ad parabolum; if an ellipse, locus ad ellip-
sin; and so of the rest of the conic sections.