Locally closed subset

In topology, a subset \( A \) of a topological space \( X \) is called **locally closed** if it can be expressed as the intersection of an open set and a closed set in \( X \). More formally, a subset \( A \subseteq X \) is locally closed if there exists an open set \( U \subseteq X \) and a closed set \( C \subseteq X \) such that: \[ A = U \cap C.