x1 is a mathematical structure defined on underlying structure/set/parts x2 with properties/rules/relations/operands/functions/substructures x3 in mathematics x4.
Includes algebraic structures such as magmas etc., ordered sets of various forms and with various order relations, sets with other relations (which could be represented via graphs/networks), topological spaces, metric spaces, etc. Any mathematical structure falls into the semantic scope of this word.