Symbols:Number Theory

Divides, Divisor, Factor

 * $x\backslash y$

This means "$x$ is a divisor (or factor) of $y$", or "$x$ divides $y$".

$\backslash$ is gaining in popularity over $\mid$, since many mathematicians are of the opinion that $\mid$ is overused, and hence confusing.

The $\LaTeX$ code for $x\backslash y$ is x \backslash y.

See Set Operations and Relations: Set Difference for an alternative definitions of this symbol.

Does Not Divide, Is Not a Divisor or Factor

 * $x \nmid y$

This means $x$ is not a divisor of $y$.

The $\LaTeX$ code for $x \nmid y$ is x \nmid y.

This symbol is preferable to $x \not \backslash y$ (x \not \backslash y) and $x \not | y$ (x \not | y) due to the somewhat confusing appearance of these symbols.

Ceiling

 * $\left\lceil{x}\right\rceil$

This represents the smallest integer greater than or equal to $x$. (See Definition:Ceiling Function).

The $\LaTeX$ code for $\left\lceil{x}\right\rceil$ is \left\lceil{x}\right\rceil.

Note that the \left and \right, as with other surrounding symbols such as parenthesis and brackets, adjust the size of the symbols as appropriate, for example with $\left\lceil {\frac{\frac x y}{\frac a b}} \right\rceil$. On ProofWiki, the delimiters \left and \right</tt> are mandatory.

Floor

 * $\left\lfloor{x}\right\rfloor$ or $\left[{x}\right]$

This represents the greatest integer less than or equal to $x$. (See Definition:Floor Function).

The $\LaTeX$ code for $\left\lfloor{x}\right\rfloor$ is \left\lfloor{x}\right\rfloor</tt>.

$\left\lfloor{x}\right\rfloor$ is gaining in popularity over the more traditional $\left[{x}\right]$, due to the already varied uses of square brackets.

Note that the \left</tt> and \right</tt>, as with other surrounding symbols such as parenthesis and brackets, adjust the size of the symbols as appropriate, for example with $\left\lfloor {\frac{\frac x y}{\frac a b}} \right\rfloor$. On ProofWiki, the delimiters \left</tt> and \right</tt> are mandatory.

= Deprecated Symbols =

Divisor

 * $x \mid y$

This means $x$ is a divisor of $y$.

$\mid$ has been (or is in the process of being) superseded by $\backslash$, which is becoming increasingly popular since many mathematicians are of the opinion that $|$ is overused, and hence a possible cause for confusion.

The $\LaTeX$ code for $\mid$ is |</tt>, \vert</tt> or \mid</tt>.

In the context of computer languages, $\mid$ is frequently called "pipe" from its use in Unix. This name is catching on in general mathematics.

Floor, or Integral Part

 * $\left[{x}\right]$

This represents the greatest integer less than or equal to $x$. (See Definition:Floor Function).

The $\LaTeX$ code for $\left[ x\right]$ is \left[{x}\right]</tt>.

$\left[{x}\right]$ has been (or is in the process of being) superseded by $\left\lfloor{x}\right\rfloor$, due to the already varied uses of square brackets.