Rho (ρ) in LaTeX
In LaTeX maths mode, \rho produces the lowercase Greek letter rho (ρ) and \varrho produces the curly variant (ϱ). Uppercase Rho is identical to a Latin capital P, so there is no \Rho command.
LaTeX command
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Rho, \rho, is a P-shaped letter with a descending tail. In physics it denotes density, both mass and charge density, and electrical resistivity; in statistics it is a population correlation coefficient, including Spearman's rank correlation; and in linear algebra \rho(A) is the spectral radius of a matrix. It is also the radial coordinate in cylindrical and plane-polar systems.
The variant \varrho gives a more rounded, cursive rho (ϱ). Use it when you need a rho distinct from \rho on the same page, or to match a text's convention. Both forms are maths-mode only and render italic by default; \varrho needs no special package in KaTeX.
There is no uppercase command, because the capital Greek Rho is drawn exactly as a Roman P; type P, or \mathrm{P} for an upright roman capital. Take care to distinguish \rho (ρ) from a lowercase Latin p, which sits differently on the baseline.
Other forms
\rholowercase rho\varrhocurly / variant formExamples
$\rho$lowercase rho inline
$\rho = \frac{m}{V}$density as mass over volume
$\rho(A) = \max_i |\lambda_i|$the spectral radius of a matrix
$\varrho$the curly variant
Tips and common mistakes
\varrhois the curly variant (ϱ); reach for it when you need a rho distinct from\rho.- There is no
\Rho; uppercase Greek Rho is a Latin P, so type P. - Both rho commands are maths-mode only; wrap them in .
- Do not confuse
\rho(ρ) with a Latin p; the Greek form has a rounder bowl and a straight descender. - In statistics reserve
\rhofor the population correlation and r for the sample estimate.
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Convert your maths to LaTeX →FAQ
Is there a capital rho command?
No. Uppercase Greek Rho is identical to the Latin P, so LaTeX has no \Rho; type P, or \mathrm{P} for an upright shape.
How do I write the curly rho?
Use \varrho, which renders ϱ. It works in KaTeX and standard LaTeX without extra packages.
What does rho mean in statistics?
Rho (ρ) is the population correlation coefficient; Spearman's rank correlation is also written ρ. It measures the strength of association between two variables.