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The seventeenth Greek letter, used for density and resistivity.
Also known as: Greek letter rho, Rho symbol, Density symbol, ρ
Rho is the conventional letter for density — mass per unit volume in physics, and by extension charge density and electrical resistivity. It is one of the more consistent letters: wherever it appears, something is being measured per unit of something else.
Is a letter of the Greek alphabet before it is a symbol: what it denotes is fixed by the field it appears in, not by the character itself. The uses below are the documented conventions, not competing definitions.
Contexts: Mathematics
In physics, denotes density — mass per unit volume.
Contexts: Mathematics
In electromagnetism, denotes electrical resistivity, or charge density.
Contexts: Mathematics
In statistics, denotes a population correlation coefficient.
Contexts: Mathematics
In polar coordinates, denotes the radial distance from the origin.
Contexts: Mathematics
Is drawn almost identically to the Latin letter p and is frequently mistyped as one, which silently changes the meaning in any formula that also uses p for pressure or probability.
Contexts: Mathematics
A rounded bowl on the right of a vertical stroke that descends below the writing line, like a lowercase p.
Electrical resistivity and conductivity are reciprocals of one another: rho is one divided by sigma.