Universal Property of Direct Sum of Modules

Theorem
Let $R$ be a ring.

Let $N$ be an $R$-module.

Let $\family {M_i}_{i \mathop \in I}$ be a family of $R$-modules.

Let $M = \ds \bigoplus_{i \mathop \in I} M_i$ be their direct sum.

Let $\family {\psi_i}_{i \mathop \in I}$ be a family of $R$-module morphisms $M_i \to N$.

Then there exists a unique morphism:


 * $\Psi: M \to N$

such that:
 * $\forall i: \psi_i = \Psi \circ \iota_i$

where $\iota_i: M_i \to M$ is the $i$th canonical injection.

Also see

 * Universal Property of Direct Product of Modules