The Science of Living Things series demonstrates that Bobbie Kalman and her staff have turned out yet another informative and finely produced series of books. . . . this whole series would make a welcome addition to the elementary school library -- Kay Lehr, Fort Rouge School, Manitoba, Jan. 1999.
perpendicularity - the quality of being at right angles to a given line or plane (especially the plane of the horizon) oblongness, rectangularity - the property of being shaped like a rectangle.
definition : orthogonality In mathematics, orthogonality is the relation of two lines at right angles to one another (perpendicularity), and the generalization of this relation into n dimensions; and to a variety of mathematical relations thought of as describing non-overlapping, uncorrelated, or independent objects of some kind.