A morphism 
in a category is an epimorphism
if, for any two morphisms 
,
implies 
. In the categories of sets,
groups, modules, etc., an epimorphism is the same as a surjection,
and is used synonymously with "surjection" outside of category
theory.
Epimorphism
See also
Category, Monomorphism, Morphism, SurjectionExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Epimorphism." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Epimorphism.html