Lesson 6

We say that the orders \((P, \preceq_{P})\) and \((Q, \preceq_{Q})\) are isomorphic if there exists a bijection \(\phi \colon P \to Q\) such that \(x_{1} \preceq_{P} x_{2}\) is equivalent to \(\phi(x_{1}) \preceq_{Q} \phi(x_{2})\) (for all \(x_{1}, x_{2}\)).