Rho Symbol ρ — Copy, Paste & Learn
ρ
Lowercase Rho (U+03C1)
Ρ
Uppercase Rho (U+03A1)
What Does the Rho Symbol Mean?
Rho (ρ, Ρ) is the 17th letter of the Greek alphabet. In the Greek numeral system, it has a value of 100. The lowercase rho is instantly recognizable in science — it is the standard symbol for density, one of the most fundamental physical properties.
Rho in Physics
Density
The most common use of ρ in physics is for density — mass per unit volume (ρ = m/V). Water has a density of approximately 1000 kg/m³. Air at sea level has a density of about 1.225 kg/m³. Understanding density is fundamental to fluid mechanics, material science, and engineering.
Resistivity
In electrical engineering, ρ represents electrical resistivity — how strongly a material opposes the flow of electric current. Copper has a resistivity of about 1.68 × 10⁻⁸ Ω⋅m, which is why it is widely used in electrical wiring.
Charge Density
In electromagnetism, ρ denotes charge density — the amount of electric charge per unit volume. This appears in Gauss's law and Maxwell's equations.
Rho in Statistics
Spearman's Rank Correlation (ρ)
In statistics, ρ represents the population correlation coefficient. Spearman's rho measures the strength and direction of the monotonic relationship between two ranked variables. It ranges from -1 (perfect negative correlation) to +1 (perfect positive correlation).
Rho in Finance
In options pricing, rho measures the sensitivity of an option's price to changes in the risk-free interest rate. It is one of the "Greeks" used in financial derivatives trading.
Rho in Mathematics
- Spectral radius: The maximum absolute value of eigenvalues of a matrix
- Apportionment: Used in the Balinski-Young theorem about fair representation
- Fano's inequality: Information theory uses ρ for the probability of error
Unicode Details
| Symbol | Name | Unicode | HTML Entity |
|---|---|---|---|
| ρ | Greek Small Letter Rho | U+03C1 | ρ |
| Ρ | Greek Capital Letter Rho | U+03A1 | Ρ |
| ϱ | Rho Symbol (Variant) | U+03F1 | ϱ |
How to Type Rho
Windows
Hold Alt and type 236 on the numeric keypad for lowercase ρ.
Mac
There is no direct Option shortcut for rho. Use the Greek keyboard layout or the Character Viewer (Control + Command + Space).
LaTeX
Use \\rho for lowercase ρ and \\varrho for the variant form ϱ.
Related Symbols
- Pi (π) — The circle constant, adjacent letter in the Greek alphabet
- Sigma (Σ) — Summation and standard deviation
- Delta (Δ) — Change or difference
- Theta (θ) — Angles and temperature
Quick copy: ρ (lowercase) · Ρ (uppercase) · ϱ (variant)
Last updated: April 2026