Finite and Infinite

• Finite and Infinite #Card
  • • A set $X$ is finite if every injection $f : X \to X$ is a surjection. Otherwise it is infinite. - $\text{card } \emptyset = 0$.

Back

• A set $X$ is finite if every injection $f : X \to X$ is a surjection. Otherwise it is infinite.
• $\text{card } \emptyset = 0$.

Lean

Finite X / Infinite X