# Definition:Divisor of Polynomial

## Definition

Let $D$ be an integral domain.

Let $D \sqbrk x$ be the polynomial ring in one variable over $D$.

Let $f, g \in D \sqbrk x$ be polynomials.

Then:

**$f$ divides $g$****$f$ is a divisor of $g$****$f$ is a factor of $g$****$g$ is divisible by $f$**

- $\exists h \in D \sqbrk x : g = f h$

This is denoted:

- $f \divides g$

### Notation

The conventional notation for **$x$ is a divisor of $y$** is "$x \mid y$", but there is a growing trend to follow the notation "$x \divides y$", as espoused by Knuth etc.

From Ronald L. Graham, Donald E. Knuth and Oren Patashnik: *Concrete Mathematics: A Foundation for Computer Science* (2nd ed.):

*The notation '$m \mid n$' is actually much more common than '$m \divides n$' in current mathematics literature. But vertical lines are overused -- for absolute values, set delimiters, conditional probabilities, etc. -- and backward slashes are underused. Moreover, '$m \divides n$' gives an impression that $m$ is the denominator of an implied ratio. So we shall boldly let our divisibility symbol lean leftward.*

An unfortunate unwelcome side-effect of this notational convention is that to indicate non-divisibility, the conventional technique of implementing $/$ through the notation looks awkward with $\divides$, so $\not \! \backslash$ is eschewed in favour of $\nmid$.

Some sources use $\ \vert \mkern -10mu {\raise 3pt -} \ $ or similar to denote non-divisibility.

## Also see

## Sources

- 1969: C.R.J. Clapham:
*Introduction to Abstract Algebra*... (previous) ... (next): Chapter $8$: Field Extensions: $\S 37$. Roots of Polynomials: Theorem $70$