In category theory a so-called homset is the type of arrows between two objects: Given category C:SetGiven A,B:CC[A,B]={f:arr(C).dom(f)=A∧dom(f)=B} Duplicate Content 1 In a category, a hom-set is the type of all morphisms between two fixed objects. Written C[a,b], Hom[a,b], a→Cb.