dimension, in mathematics, number of parameters or coordinates required to describe points in a mathematical object (usually geometric). The space we inhabit, having height, width, and depth, is three-dimensional; a plane or surface is two-dimensional; a line or curve is one-dimensional; and a point is zero-dimensional. By means of a coordinate system, e.g. CARTESIAN COORDINATES, one can specify any point with respect to a chosen origin (and coordinate axes through the origin, in the case of two or three dimensions). By analogy, and ordered set of four, five, or more numbers is defined as representing a point in a space of four, five, or more dimensions.

--The Concise Columbia Encyclopedia