Density of mass

• Density, mass per unit volume
  • Bulk density, mass of a particulate solid or powder divided by the volume it occupies
  • Particle density (packed density) or true density, density of the particles that make up a particulate solid or a powder
  • Neutral density, mass density of seawater
• Area density or surface density, mass over a (two-dimensional) area
• Linear density, mass over a (one-dimensional) line
• Relative density or specific gravity, a measure of density in comparison to the density of something else
  • Vapour density, a relative density used for gases

Densities of other entities

• Mass-specific quantity, the quotient of a physical quantity and mass
  • Specific energy, energy per unit mass

• Volume-specific quantity, the quotient of a physical quantity and volume
  • Charge density, the electric charge per volume
  • Energy density, potential energy per unit volume
  • Force density, force per unit volume
  • Power density, power per unit volume
  • Particle density (particle count), number of particles per unit volume

• Area-specific quantity, the quotient of a physical quantity and area
  • Current density, the ratio of electric current to area
  • Surface power density, power per unit area

Other:

• Number density, number of particles per unit volume, area, or length
• Optical density, the absorbance of a material
  • Densitometry, measuring the optical density of photographic paper, photographic film and x-ray film

Probability and measure theory

• Probability density function, a function which maps probabilities across the real line and whose integral is 1
  • Density estimation is the construction of an estimate of a probability density function
  • Kernel density estimation, used in statistics to estimate a probability density function of a random variable
• Lebesgue's density theorem

Number theory

• Schnirelmann density
• Natural density (also called asymptotic density)
• Dirichlet density

Geometry

• Packing density
• Density (polytope)
• Density on a manifold
• Tensor density in differential geometry

Topology

• Dense set and nowhere dense set
• Dense-in-itself is a set that contains no isolated points

Other fields

• Density (graph theory), the fraction of possible edges that exist in a graph
• Dense order in order theory
• A coinitial subset in the mathematical theory of forcing, in set theory
• Dense submodule in abstract algebra