Source : Webster's Revised Unabridged Dictionary (1913)

Structural \Struc"tur*al\, a.
   1. Of or pertaining to structure; affecting structure; as, a
      structural error.

   2. (Biol.) Of or pertaining to organit structure; as, a
      structural element or cell; the structural peculiarities
      of an animal or a plant.

   {Structural formula}. (Chem.) See {Rational formula}, under
      {Formula}.

Source : WordNet®

structural formula
     n : an expanded molecular formula showing the arrangement of
         atoms within the molecule