\begin{definition}[Definition:Root of Polynomial]
Let $R$ be a commutative ring with unity.
Let $f \in R \sqbrk x$ be a polynomial over $R$.
A '''root''' in $R$ of $f$ is an element $x \in R$ for which $\map f x = 0$, where $\map f x$ denotes the image of $f$ under the evaluation homomorphism at $x$.
\end{definition}