Definition:Integral Multiple

Definition

Rings and Fields

Let $\struct {F, +, \times}$ be a ring or a field whose zero is $0_F$.

Let $a \in F$.

Let $n \in \Z$ be an integer.

Then $n \cdot a$ is an integral multiple of $a$ where $n \cdot a$ is defined as:

$n \cdot a := \begin {cases}

0_F & : n = 0 \\ \paren {\paren {n - 1} \cdot a} + a & : n > 1 \\ \size n \cdot \paren {-a} & : n < 0 \\ \end {cases}$ where $\size n$ is the absolute value of $n$.

Real Numbers

This concept is often seen when $F$ is the set of real numbers $\R$.

Let $x, y \in \R$ be real numbers.

Then $x$ is an integral multiple of $y$ if and only if $x$ is congruent to $0$ modulo $y$:

$x \equiv 0 \pmod y$

That is:

$\exists k \in \Z: x = 0 + k y$

Also see

Compare divisor, in which all the numbers involved are integers (or at least, elements of an integral domain).