\begin{definition}[Definition:Degree of Polynomial/Null Polynomial/Integral Domain]
Let $\struct {R, +, \circ}$ be a commutative ring with unity whose zero is $0_R$.
Let $\struct {D, +, \circ}$ be an integral subdomain of $R$.
For arbitrary $x \in R$, let $D \sqbrk x$ be the ring of polynomials in $x$ over $D$.
The null polynomial $0_R \in D \sqbrk x$ does ''not'' have a degree.
\end{definition}