LOCUS (

See also:

• LAT

Lat. for "

See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place "; in Gr. rinros)  , a geometrical term, the invention of the notion of which is attributed to Plato . It occurs in such statements as these: the locus of the points which are at the same distance from a fixed point, or of a point which moves so as to be always at the same distance from a fixed point, is a circle; conversely a circle is the locus of the points at the same distance from a fixed point, or of a point moving so as to be always at the same distance from a fixed point; and so in general a curve of any given kind is the locus of the points which satisfy, or of a point moving so as always to satisfy, a given condition . The theory of loci is thus identical with that of curves (see CURVE and GEOMETRY: § Analytical) . The notion of a locus applies also to solid geometry . Here the locus of the points satisfying 'a single (or onefold) condition is a surface; the locus of the points satisfying two conditions (or a twofold condition) is a curve in space, which is in general a twisted curve or curve of double curvature .