Definition:Submodule

Definition
Let $\struct {R, +, \circ}$ be a ring.

Let $\struct {G, +_G}$ be an abelian group.

Let $\struct {G, +_G, \circ_G}_R$ be an $R$-module.

Let $H \subseteq G$ be a subset of $G$ which is closed for scalar product:


 * $\forall \lambda \in R, x \in H: \lambda \circ x \in H$

Let $\struct {H, +_H, \circ_H}_R$ be an $R$-module where:
 * $+_H$ is the restriction of $+_G$ to $H \times H$
 * $\circ_H$ is the restriction of $\circ_G$ to $R \times H$.

Then $\struct {H, +_H, \circ_H}_R$ is a submodule of $\struct {G, +_G, \circ_G}_R$.