\binom - LaTeX binomial coefficient command

\binom{n}{k}

Renderer support

Package	MathJax	KaTeX	XeTeX
`ams`	MathJax: Full	KaTeX: Full	XeTeX: Full

Syntax#

\binomm{a}math contentm{b}math content

Argspec m m — two mandatory arguments. Reading argspecs

\binom{n}{k}

\sum_{k=0}^n \binom{n}{k} = 2^n

\binom follows the current style; \dbinom / \tbinom lock display or text size.

\tbinom{n}{k}

TeXForm parses this entry as prefix syntax; the package determines its argument specification.

\genfrac{(}{)}{0}{}{#1}{#2}exact
This AMS mapping fixes \genfrac to use ( and ) delimiters, linethickness 0, and empty style.
n \choose kapproximate
\choose is a TeX primitive with different grouping scope; \binom is preferred in LaTeX

`ams`
Input	Case	MathJax	KaTeX	XeTeX
`\binom{a}{b}`	Positive · baseline	Pass	Pass	Pass
`\binom a{b}`	Positive · bare[0]	Pass	Pass	Pass
`\binom{a}b`	Positive · bare[1]	Pass	Pass	Pass