The Greek letter (rho) is used in math as a variable and in physics to represent density.
Symbol  Format  Data 

ρ  Unicode 

TeX 


SVG 
The Latin Alphabet is a collection of 26 symbols that form the basis of the English language. The alphabet's symbols are used throughout mathematics to represent variables, constants, and coeffecients.
The capital Greek letter Ρ (captial rho).