\Zon"al\, a. [L. zonalis.]
Of or pertaining to a zone; having the form of a zone or
zones.
{Zonal equation} (Crystallog.), the mathematical relation
   which belongs to all the planes of a zone, and expresses
   their common position with reference to the axes.
{Zonal structure} (Crystallog.), a structure characterized by
   the arrangements of color, inclusions, etc., of a crystal
   in parallel or concentric layers, which usually follow the
   outline of the crystal, and mark the changes that have
   taken place during its growth.
{Zonal symmetry}. (Biol.) See the Note under {Symmetry}.