Definition:Constant Polynomial/Definition 3

Definition
Let $R$ be a commutative ring with unity.

Let $P \in R \left[{x}\right]$ be a polynomial in one variable over $R$.

The polynomial $P$ is a constant polynomial it is in the image of the canonical embedding $R \to R \left[{x}\right]$.

Also see

 * Equivalence of Definitions of Constant Polynomial