Structure: Entity made up of
diverse parts that remains the same entity if some of its parts are
replaced by other parts of the same kind.
This is a fundamental
stipulative definition of a fundamental
idea that is fleshed out in various ways in various disciplines, like
logic, mathematics and linguistics. Structures in some sense are often
supposed to be part of reality, and
sometimes reality or some part of it is considered to be made up of
nothing but structures.