👉 In algebraic topology, an epimorphism is a morphism of topological spaces that is both injective and surjective. This means that it maps open sets to open sets and closed sets to closed sets, respectively. For instance, consider two topological spaces X and Y with a continuous map f: XY. We can define the image of an open set U in X by f−1(U) = {x ∈ X | f(x) ∈ U}. Similarly, we can define
