"Particle Number Density"@en . . . . . . . . . "\\(n = \\frac{N}{V}\\), where \\(N\\) is the number of particles in the 3D domain with the volume \\(V\\)."^^ . "n" . "http://en.wikipedia.org/wiki/Particle_number#Particle_number_density"^^ . . "http://www.iso.org/iso/catalogue_detail?csnumber=31895"^^ . "The \"Particle Number Density\" is obtained by dividing the particle number of a system by its volume." .