Two nets given in the same domain $G$ of a two-dimensional manifold, where at each point $x\in G$ the tangent directions of one net harmonically subdivide the tangent directions of the other. Thus, for instance, the asymptotic net on a surface in a Euclidean space is apolar with respect to the net of curvature lines (cf. Curvature lines, net of).
Apolar nets. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Apolar_nets&oldid=33094