Caldas, MiguelJafari, SaeidMoshokoa, Seithuti P.2025-01-072025-01-072006-04-061225-1763 (P)2234-3024 (E)https://doi.org/10.4134/CKMS.2010.25.4.623https://hdl.handle.net/20.500.14519/1104Nakaoka and Oda ([1] and [2]) introduced the notion of maximal open sets and minimal closed sets in topological spaces. In this paper, we introduce new classes of sets called maximal θ-open sets, minimal θ-closed sets, θ-semi maximal open and θ-semi minimal closed and investigate some of their fundamental properties.623-628 PagesenAttribution-NonCommercial-ShareAlike 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-sa/4.0/Topological spaceMaximal open setsMinimal closed setsθ-open setsθ-semi maximal open setsArticle