The Greek letter Rho (Ρ) is the 17th letter of the Greek alphabet. It is often used to represent the sound 'r' in words such as 'RHETORIC' and 'RHYTHM'. In Greek mythology, Rho is associated with Poseidon, the god of the sea. It is also associated with the constellation of Pisces, which is represented by two fish swimming in opposite directions. In mathematics, Rho is used to represent the radius of a circle.