Rho (upper case Ρ, lower case ρ) is a letter of the Greek alphabet. See Rho (letter).\n#The lower-case letter ρ is used as the symbol for the radius in a polar coordinate system in mathematics.\n#The lower-case letter ρ is used as the symbol for the density of a material in physics.\n#The lower-case letter ρ is used as the symbol for the resistivity of a material in physics.
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"Why don't you write books people can read?"
- Nora Joyce to her husband James (1882-1941)
