a figure having nine sides and angles. In a regular nonagon, or that whose angles and sides are all equal, if each side be 1, its area will be Nonagon 6.1818242=π/2 of the tangent of 70°, to the radius 1.

NON, Cape, a promontory on the west coast of Africa, opposite to the Canary islands. W. Long. 12. O. N. Lat. 44. 28.