# Just a simple question. What does Eisenbud mean by ( x : y ) where x , y

Just a simple question. What does Eisenbud mean by $\left(x:y\right)$ where $x,y\in R$ a ring. An example on this is in the section 17 discussing the homology of the koszul complex. I assume it's something along the lines of $\left\{r\mid ax=ry\right\}$ for some $a\in R$.
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Jamiya Costa
Eisenbud introduces this notation in section 0.3. If $I$ and $J$ are two ideals in $R$, then
$\left(I:J\right)=\left\{r\in R\mid r\cdot J\subseteq I\right\}.$
In this case, $I=\left(x\right)$, $J=\left(y\right)$.