Density (disambiguation)

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
  • The Planck density, the derived unit of density in the Planck unit system (1 Planck mass divided by 1 Planck volume)
• 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

• Number density, number of particles per unit volume, area, or length
• Current density, the ratio of electric current to area
• Charge density, the electric charge per volume
• Energy density, potential energy per unit volume or mass, depending on context
• Force density, force per unit volume
• Optical density, the absorbance of a material
  • Densitometry, measuring the optical density of photographic paper and film and x-ray film
• Particle density (particle count), number of particles per unit volume

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

• Spiritual density, levels of spiritual evolution, planes of existence, or "dimensions" in The Law of One
• 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)