Rho (Ρ or ρ) is a letter of the Greek alphabet. Rho or RHO also may refer to: Science and medicine Rho family of GTPases RHOA RHOB RhoC RHO (gene), or Rhodopsin ρ as a conventional symbol in mathematics A length coordinate in coordinate systems with both length and angle coordinates: Polar coordinate system Spherical coordinate system Cylindrical coordinate system Toroidal coordinate system Toroidal and poloidal coordinates of the Earth's magnetic field Spectral radius of a square matrix Pollard's rho algorithm Pollard's rho algorithm for logarithms Prime constant Plastic number in physics Density of a material Volume charge density Resistivity of a material Rho meson in biology Rho factor protein in RNA transcription termination Ecology, population damping ratio where ρ = λ1 / |λ2|. in statistics Spearman's rank correlation coefficient Pearson product-moment correlation coefficient in other fields The reaction constant in the Hammett equation in chemistry Rho (finance) Toponyms Rho, Lombardy, a town in Italy Rho Island, a.k.a. Ro, Greece Rho River, tributary of the Dora di Bardonecchia, Italy Acronyms and abbreviations RHO Right-Hand Opponent, in contract bridge Red Hot Organization, HIV/AIDS-related charity Rhodes International Airport, in Greeter using People Giacomo Rho (1593-1638), Italian Jesuit missionary in China See also Ro (disambiguation)