Density (disambiguation)

From Wikipedia, the free encyclopedia

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

In physics:

• Density, mass per volume
  • Area density, mass over a (two-dimensional) area
  • Linear density, mass over a (one-dimensional) line
  • Planck density, Planck mass per Planck length
  • Specific gravity, a dimensionless ratio based on the density of a substance to the density of water
• Relative density, a measure of density in comparison to the density of something else
  • Vapour density, a relative density used for gases
• 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
• Information density, the amount of information compared to many units
• Optical density, the absorbance of an element

In mathematics:

• Dense set and nowhere dense set in topology
• Schnirelmann density in number theory
• Natural density (also called asymptotic density) in number theory
• Lebesgue density in 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
• Tensor density in differential geometry
• Density in graph theory, the fraction of possible edges that exist in a graph
• Dense order in order theory
• Dense-in-itself, in geometry, is a set that contains no isolated points
• In forcing (mathematics), a subset D of a forcing notion (P, ≤ ) is called dense in P if for any p in P there is d in D with d≤p

In other scientific fields:

• Population density, population per unit area
• Computer storage density, bits (how computers store information) over an amount of area or volume

Density can also refer to:

• Spiritual density, states of being for various planes of existence