An D21: Algebraic structure $M = (X, +, \times)$ is a module over $R$ if and only if
| (i) | $G = (X, +)$ is an D23: Abelian group |
| (ii) | $\times : R \times G \to G$ is a D274: Left ring action of $R$ on $G$ |
| (i) | $G = (X, +)$ is an D23: Abelian group |
| (ii) | $\times : R \times G \to G$ is a D274: Left ring action of $R$ on $G$ |