# Definition:Polynomial Ring/Monoid Ring on Natural Numbers

## Definition

Let $R$ be a commutative ring with unity.

Let $\N$ denote the additive monoid of natural numbers.

Let $R \left[{\N}\right]$ be the monoid ring of $\N$ over $R$.

The **polynomial ring over $R$** is the ordered triple $\left({R \left[{\N}\right], \iota, X}\right)$ where:

- $X \in R \left[{\N}\right]$ is the standard basis element associated to $1\in \N$.
- $\iota : R \to R \left[{\N}\right]$ is the canonical mapping.

## Notation

It is common to denote a **polynomial ring** $\left({S, \iota, X}\right)$ over $R$ as $R \left[{X}\right]$, where $X$ is the indeterminate of $\left({S, \iota, X}\right)$.

The embedding $\iota$ is then implicit.