A sequence ${x_n}_{n\in\mathbb N}$ in a metric space $(X,\rho)$ is Cauchy if for all $\varepsilon > 0$, there exists $n_0 > 0$ such that $\rho(x_n, x_m) < \varepsilon$ for all $m,n \geq n_0$
Wikidata ID: Q217847