Let $X$ be a topological space. A set $A\subset X$ is nowhere dense in $X$ if for every nonempty open subset $G\subset X$, there exists a nonempty open subset $H\subset G$ such that $A\cap H=\emptyset$.
Equivalently, a set $A\subset X$ id nowhere dense in $X$ if its closure has empty interior.
Wikidata ID: Q1991405