Let $X$ be a metric space with $A \subset X$. Let $\mu$ be the Lebesgue measure. A collection $\mathcal V$ of sets covering $A$ is a Vitali covering if for each $x \in A$ and $\varepsilon > 0$, there exists $U \in \mathcal V$ such that $x \in U$, and the diameter of $U$ is nonzero and less than $\varepsilon$.
Wikidata ID: Q3229352