a. [ L. zonalis. ] Of or pertaining to a zone; having the form of a zone or zones. [ 1913 Webster ]

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. [ 1913 Webster ]