Surface tension is the property of a liquid which enables it to resist tensile stress. Surface tension is denoted by σ (sigma). Surface tension is expressed in N/m (Newton/meter).

Density or mass density is defined as the mass per unit volume of a liquid at a standard temperature and pressure. Density or mass density is usually denoted by ρ(rho).

Density or mass density is expressed in kg/m³.

Mathematically, density or mass density, ρ=m/V, where
m = Mass of the liquid, and
V = Volume of the liquid.