Definition 10.88.2. Let $f: M \to N$ and $g: M \to M'$ be maps of $R$-modules. Then we say $g$ dominates $f$ if for any $R$-module $Q$, we have $\mathop{\mathrm{Ker}}(f \otimes _ R \text{id}_ Q) \subset \mathop{\mathrm{Ker}}(g \otimes _ R \text{id}_ Q)$.

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).