Pointed category

A pointed category has a zero object, hence a distinguished zero morphism between every pair of objects.

A morphism $e:A\to B$ in a pointed category is pseudo-epic when, for every $t:B\to Z$, the equation $te=0$ forces $t=0$. If a categorical cokernel exists, this is equivalent to that cokernel having a zero object as codomain. Indeed all zero composites then factor uniquely through zero; conversely the cokernel itself must be zero, and being both zero and epic forces its codomain to have identity zero, hence be a zero object. Every epimorphism is pseudo-epic. In a preadditive category, subtraction shows the converse: $ue=ve$ implies $(u-v)e=0$, hence $u=v$. In a general pointed category no subtraction is available.

In a pointed category with categorical kernels and categorical cokernels, where every monomorphism is normal, every $h$ factors through $i=\ker (\mathrm{coker}h)$ as $h=ie$, with $e$ a pseudo-epimorphism. If $te=0$, write $k=\ker t$. Then $e$ factors through $k$, and the monic $ik$ is a categorical kernel of some $q$ by normality. Since $qh=0$, the cokernel of $h$ forces $qi=0$. Hence $i$ factors through $ik$, forcing $k$ to be an isomorphism and therefore $t=0$. This establishes the factorization without assuming the stronger abelian category axioms.

A zero object is both an initial object and a terminal object. In a pointed category, the composite through the zero object is the zero morphism $0_{A,B}:A\to B$.

In a pointed category, the zero morphism $0_{A,B}:A\to B$ is the composite through its zero object. Composition on either side by any morphism remains zero. In a commutative-monoid enrichment on a pointed category, the additive zero must coincide with this zero morphism: morphisms to and from the zero object belong to singleton hom-sets.

The kernel of $f:A\to B$ is the universal morphism $k:K\to A$ satisfying $fk=0$. It is the equalizer of $f$ and the zero morphism.

The cokernel of $f:A\to B$ is the universal morphism $q:B\to Q$ satisfying $qf=0$. It is the coequalizer of $f$ and the zero morphism.

In a pointed category, a pushout in a category of $f$ and $f^{\prime }$ induces an isomorphism between their categorical cokernels, when those cokernels exist. Push out the cokernel map of $f$ together with the zero map, then factor through the cokernel of $f^{\prime }$. Cokernel and pushout uniqueness prove that this map is inverse to the induced comparison. No abelian hypothesis is needed.

A normal monomorphism is a monomorphism that is the kernel in a category of some morphism. In a pointed category with kernels and cokernels, a monomorphism is normal exactly when it is the kernel of its own cokernel.

In an additive category with finite categorical limits and colimits in which every epimorphism is a conormal epimorphism, closure of normal monomorphisms under composition forces every monomorphism to be normal. To prove this, write a monomorphism $m$ as $kg$, where $k=\ker \mathrm{coker}m$, and put $l=\ker \mathrm{coker}g$. If $kl=\ker t$ were normal, $tm=0$ would force $tk=0$, hence $l$ would be an isomorphism. This makes $\mathrm{coker}g=0$, so $g$ is epic as well as monic. An epic monomorphism which is a cokernel is invertible, forcing $m$ to be normal. Contrapositively, any failure of normality provides two normal monomorphisms whose composite is not normal.

A conormal epimorphism is an epimorphism that is the cokernel in a category of some morphism. It is the concept dual to a normal monomorphism.