Density

Look up density in Wiktionary, the free dictionary.

Look up dense in Wiktionary, the free dictionary.

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 of mass:

• 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

In physics, densities of entities other than mass:

• 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 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's density theorem 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-in-itself, in geometry, is a set that contains no isolated points
• Dense order in order theory
• Dense (= Coinitial) subset of a poset in order theory
• Density of a polytope in geometry

In other scientific fields:

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

Density can also refer to:

• Plane (esotericism) (spiritual density), states of being for various planes of existence
• Stupidity, a stupid person is sometimes referred to as being "dense"

See also

• Concentration
• Flux
• Intensity (physics)

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