Role of θ-closure in the study of H-closed spaces

The concept of an H-closed space is a generalization of the concept of compactness. In this study we focus on the role of θ-closure of a set in the study of H-closed spaces. The θ-closure was introduced by Velicko in 1966 to give characterizations of H-Closed spaces. It later became an object of study on its own, along with the associated concepts of θ-closed and θ-open sets. It was discovered that the θ-open sets generate the Tθ topology, which became another area of research.