Form is defined by opposition to content which is foreign to it, but structure has no distinct content. It is the content itself apprehended in a logical organization conceived as a property of the real.
Lévi-Strauss, Claude. “La structure et la forme. Réflexions au un ouvrage de Vladimir Propp,” Cahiers de l’I.S.E.A. 99 série M, No.7 (March 1960).