# zero divisor
## English
### Alternative forms

* zero-divisor

### Noun

zero divisor (plural zero divisors)
* (algebra, ring theory) An element a of a ring R for which there exists some nonzero element x ∈ R such that either ax = 0 or xa = 0.
    An idempotent element $e\neq 1$ of a ring is always a (two-sided) zero divisor, since $e(1-e)=0=(1-e)e$.
** 1984, J. B. Srivastava, “23: Projective Modules, Zero Divisors, and Noetherian Group Algebras”, in Dinesh N. Manocha, editor, Algebra and its Applications, CRC Press, page 170:Linnell [25, 1977] proved that if G is a torsion-free abelian by locally finite by super-solvable group and K is any field, then K[G] has no nontrivial zero divisors.
** 1989, K. D. Joshi, Foundations of Discrete Mathematics, New Age International, page 390:In the ring of integers, there are no zero divisors except 0. In a ring obtained from a Boolean algebra, on the other hand, every element except the identity is a zero-divisor. The concept of a zero-divisor is intimately related to cancellation law as we see n the following proposition. 1.7 Proposition: Let $R$ be a ring and $x\in R$. Then for all $y,x\in R$, either of the equations $xy=xz$ or $yx=zx$ implies $y=z$ if and only if $x$ is not a zero divisor. In other words, cancellation by an element is possible iff it is not a zero-divisor.
** 2010, Mitsuo Kanemitsu, “The Number of Distinct 4-Cycles and 2-Matchings of Some Zero Divisor Graphs”, in Masami Ito, Yuji Kobayashi, Kunitaka Shoji, editors, Automata, Formal Languages and Algebraic Systems: Proceedings of AFLAS 2008, World Scientific, page 63:In [1], Anderson and Livingston introduced and studied the zero-divisor graph whose vertices are the non-zero zero-divisors.
* (algebra, ring theory) A nonzero element a of a ring R for which there exists some nonzero element x ∈ R such that either ax = 0 or xa = 0.
** 2000, Lindsay N. Childs, A Concrete Introduction to Higher Algebra, 2nd edition, Springer, page 234:If $R$ is an integral domain, that is, has no zero divisors, then $R[x]$ also has no zero divisors.
** 2002, Paul M. Cohn, Further Algebra and Applications, Springer, page xi:An element $a$ of a ring is called a zero-divisor if $a\neq 0$ and $ab=0$ or $ba=0$ for some $b\neq 0$; if $a$ is neither 0 nor a zero-divisor, it is said to be regular (see Section 7.1). A non-trivial ring without zero-divisors is called an integral domain; this term is not taken to imply commutativity.
** 2009, Victor Shoup, A Computational Introduction to Number Theory and Algebra, 2nd edition, Cambridge University Press, page 171:If $a$ and $b$ are non-zero elements of $R$ such that $ab=0$, then $$a and $b$ are both called zero divisors. If $R$ is non-trivial and has no zero divisors, then it is called an integral domain. Note that if $a$ is a unit in $R$, it cannot be a zero divisor (if $ab=0$, then multiplying both sides of this equation by $a^{-1}$ yields $b=0$.

#### Usage notes

* The two definitions differ according to whether or not 0 is considered a zero divisor.
** The definition that includes 0 is the one preferred by Bourbaki. (See reference cited in zero divisor on Wikipedia.Wikipedia )
** Additionally, 0 may be called the trivial zero divisor.
* Related terminology:
** An element (resp. nonzero element) $a$ such that $\exists x\in R:x\neq 0\land ax=0$ is called a left zero divisor.
** An element (resp. nonzero element) $a$ such that $\exists x\in R:x\neq 0\land xa=0$ is called a right zero divisor.
** An element $a$ that is both a left zero divisor and a right zero divisor is called a two-sided zero divisor.
* Thus, a zero divisor can be (and often is) defined as any element that is either a left zero divisor or a right zero divisor.
* The term zero divisor is most relevant in the context of commutative rings (where the left–right distinction is not made).

#### Antonyms

* (antonym(s) of “any element whose product with some nonzero element is zero”): regular element

#### Hyponyms

* (any element whose product with some nonzero element is zero): trivial zero divisor
* (both senses): exact zero divisor, left zero divisor, right zero divisor, two-sided zero divisor

#### Derived terms

* zero divisor graph

#### Translations
### See also

* annihilator
* integral domain
* nilpotent

### Further reading

* Annihilator (ring theory) on Wikipedia.Wikipedia
* Topological divisor of zero on Wikipedia.Wikipedia
* Zero-divisor graph on Wikipedia.Wikipedia
* Zero-product property on Wikipedia.Wikipedia
* Zero divisor on Encyclopedia of Mathematics
* Zero Divisor on Wolfram MathWorld