Omega (Upper) in LaTeX (\Omega)

Where it is used

Uppercase Greek Omega, used for the ohm unit, sample spaces, and asymptotic lower bounds.

As a unit, \Omega is the ohm, so a resistor is 10\,\mathrm{k}\Omega; keep the number and unit separated by a thin space. Probability writes the sample space as \Omega in the triple (\Omega, \mathcal{F}, P). Algorithm analysis uses \Omega(n \log n) for a lower bound, alongside O and \Theta. Analysis often writes an open domain as \Omega \subset \mathbb{R}^n. Capital Greek letters are upright, and \varOmega gives an italic variant. Do not confuse \Omega with the mho, an inverted omega once used for siemens.

Also listed under: Units & Measurements

Minimal compilable example

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

\documentclass{article}
\begin{document}
Omega (Upper): $\Omega$

\[ R = 4.7\,\mathrm{k}\Omega, \quad (\Omega, \mathcal{F}, P) \]
\end{document}

Related symbols

• Omega\omega
• Psi (Upper)\Psi
• Psi\psi
• Chi\chi
• Phi (Upper)\Phi
• Phi\phi

Frequently asked questions

How do I write Omega (Upper) in LaTeX?

Type \Omega in math mode, for example $R = 4.7\,\mathrm{k}\Omega, \quad (\Omega, \mathcal{F}, P)$. It works in plain LaTeX without loading any package.

Which package do I need for \Omega?

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

Can I use \Omega in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\Omega$ in running text. If you only need the glyph in text, paste the Unicode character Ω instead (with XeLaTeX or LuaLaTeX and a font that has it).