density number density A ratio in which the numerator represents a count and the denominator represents an interval of space (distance, area, or volume). Brian S. Alper, Joanne Dehnbostel, Muhammad Afzal, Kenneth Wilkins, Harold Lehmann SEVCO group adapted from: The number density (symbol: n or ?N) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density. Population density is an example of areal number density. IUPAC Gold Book https://goldbook.iupac.org/terms/view/N04262 number density, n Number of particles divided by the volume they occupy. ready for release