# 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:

Look up or density in Wiktionary, the free dictionary.dense |

## 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

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