  The monumental treatise "\'El\'ements de math\'ematique" of N. Bourbaki is
based on the notion of structure and on the theory of sets. On the other hand,
the theory of categories is based on the notions of morphism and functor. An
appropriate definition of a structure in a concrete category is given in this
paper. This definition makes it possible to bridge the gap between Bourbaki's
structural approach and the categorical language.
