 Complete metric space

In plain English: the space has no visible holes. If you start walking less and less on each step, you always converge to something that also falls in the space.

One notable example where completeness matters: Lebesgue integral of $L^p$ is complete but Riemann isn't.

A **complete metric space** is a type of metric space that possesses a specific property: every Cauchy sequence in that space converges to a limit that is also within the same space. To break this down: 1. **Metric Space**: A metric space is a set \(X\) along with a metric (or distance function) \(d: X \times X \to \mathbb{R}\).