Mathematical structure is
” algebraic, topological, and order ” according to the Nicolas Bourbaki group in 1939.
Going further up in generalizations, there’s abstract structures (such as a formal language) which are defined by axioms or laws or some such similar thing that play with each other according to their own self-supporting structures (definitions are defined by definitions), which differs from a natural language whose structure is up for debate.
So there ya go.