Density and dense usually refer to a measure of how much of some entity is within a fixed amount of space. Types of density include:

Physics

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 quantities

  • Mass-specific quantity, the quotient of a physical quantity and mass
  • Volume-specific quantity, the quotient of a physical quantity and volume
  • Area-specific quantity, the quotient of a physical quantity and area.
  • Length-specific quantity, the quotient of a physical quantity and length

Other:

  • Number density, number of particles per unit volume, area, or length
  • Optical density, the absorbance of a material

Mathematics

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

Other scientific fields

  • Population density, population per unit land area
  • Urban density, in urban planning and urban design
  • Areal density (computer storage), bits (how computers store information) over an amount of area or volume
  • Nutrient density, the proportion of any array of a single nutrient or nutritional factor, or of numerous nutrients in foods, often ordered by different scalar indices

Culture and arts

  • Stupidity, a stupid person is sometimes referred to as being "dense"
  • Dense (film), a 2004 film
  • Density 21.5 – a piece of music for solo flute written by Edgard Varèse

See also

  • Concentration
  • Flux
  • Intensity (physics)