Rho in LaTeX (\rho)

Where it is used

Lowercase Greek rho, used for density, correlation coefficients, and charge density.

Physics uses \rho for mass density, \rho = m/V, and charge density in Maxwell's equations \nabla \cdot \mathbf{E} = \rho/\varepsilon_0. Statistics writes Pearson correlation as \rho_{XY} and Spearman's rank correlation as \rho. Representation theory uses \rho for a representation, and quantum mechanics uses it for a density matrix. The variant \varrho has a curly tail that some authors use to keep two meanings apart. Do not confuse \rho with the Latin p, which looks similar in many fonts.

Also listed under: Probability & Statistics

Minimal compilable example

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

\documentclass{article}
\usepackage{amsmath}
\begin{document}
Rho: $\rho$

\[ \rho_{XY} = \frac{\operatorname{Cov}(X, Y)}{\sigma_X \sigma_Y} \]
\end{document}

Related symbols

• Sigma\sigma
• Pi (Upper)\Pi
• Sigma (Upper)\Sigma
• Pi\pi
• Tau\tau
• Xi (Upper)\Xi

Frequently asked questions

How do I write Rho in LaTeX?

Type \rho in math mode, for example $\rho_{XY} = \frac{\operatorname{Cov}(X, Y)}{\sigma_X \sigma_Y}$. It works in plain LaTeX without loading any package.

Which package do I need for \rho?

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

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

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