That quality or condition of a body in virtue of which it
   exhibits opposite, or contrasted, properties or powers, in opposite, or
   contrasted, parts or directions; or a condition giving rise to a
   contrast of properties corresponding to a contrast of positions, as,
   for example, attraction and repulsion in the opposite parts of a
   magnet, the dissimilar phenomena corresponding to the different sides
   of a polarized ray of light, etc.