Definition:Zero Morphism in Preadditive Category

Definition
Let $A$ be a preadditive category.

Let $a,b$ be objects of $A$.

The zero morphism $0 : a \to b$ is the identity element of their hom set $\operatorname{Hom}(a, b)$.

Also see

 * Definition:Category with Zero Morphisms
 * Definition:Zero Object