Check in LaTeX (\check{x})

Where it is used

Sets a caron (hacek), a small v-shaped accent, over a symbol; used notably for Cech cohomology.

Algebraic topology writes \check{H}^n(X) for Cech cohomology, and some texts use \check{x} for a dual or inverse-transformed object, the opposite of a hat. The v shape distinguishes it from the round \breve and from \hat, which is an inverted v. In text, a Czech hacek like č is produced with \v{c}, not \check. The accent has fixed width; there is no standard \widecheck in core LaTeX, so over long expressions authors use a superscript instead.

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\usepackage{amssymb}
\begin{document}
Check: $\check{x}$

\[ \check{H}^{n}(X; \mathbb{Z}) \cong H^{n}(X; \mathbb{Z}) \]
\end{document}

Related symbols

• Ring\mathring{x}
• Breve\breve{x}
• Overbrace\overbrace{x+y}^{\text{sum}}
• Grave\grave{x}
• Underbrace\underbrace{x+y}_{\text{sum}}
• Acute\acute{x}

Frequently asked questions

How do I write Check in LaTeX?

Type \check{x} in math mode, for example $\check{H}^{n}(X; \mathbb{Z}) \cong H^{n}(X; \mathbb{Z})$. It works in plain LaTeX without loading any package.

Which package do I need for \check{x}?

None. \check{x} is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \check{x} in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\check{x}$ in running text.