Rho (ρ), commonly referred to as density, is a measure of how much mass is contained in a given volume. It is calculated by dividing the mass of an object by its volume, expressed in the formula ρ = m/V, where m is mass and V is volume. Density is typically measured in units such as grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³). Density plays a crucial role in various scientific fields, including physics, chemistry, and engineering. It helps determine whether an object will float or sink in a fluid, as substances with lower density than the fluid will float, while those with higher density will sink. Understanding density is essential for applications ranging from material selection to buoyancy calculations.