Definition:Monomial of Polynomial Ring/Multiple Variables/Definition 1

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

Let $I$ be a set.

Let $R[(X_i)_{i\in I}]$ be a polynomial ring in $I$ variables $(X_i)_{i\in I}$.

Let $y \in R[(X_i)_{i\in I}]$.

The element $y$ is a monomial of $R[(X_i)_{i\in I}]$ there exists a mapping $a : I \to \N$ with finite support such that:
 * $y = \displaystyle \prod_{i \in I} X_i^{a_i}$

where:
 * $\prod$ denotes the product with finite support over $I$
 * $X_i^{a_i}$ denotes the $a_i$th power of $X_i$.

Also see

 * Equivalence of Definitions of Monomial of Polynomial Ring in Multiple Variables