# 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
* 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

* Mass-specific quantity, the quotient of a physical quantity and mass
** Specific energy, energy per unit mass
* Volume-specific quantity, the quotient of a physical quantity and volume
** Charge density, the electric charge per volume
** Energy density, potential energy per unit volume
** Force density, force per unit volume
** Power density, power per unit volume
** Particle density (particle count), number of particles per unit volume
* Area-specific quantity, the quotient of a physical quantity and area
** Current density, the ratio of electric current to area
** Surface power density, power per unit area
Other:
* Number density, number of particles per unit volume, area, or length
* Optical density, the absorbance of a material
** Densitometry, measuring the optical density of photographic paper, photographic film and x-ray film

## 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