# What is density?

## Density

The mass density or density of a material is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho). Mathematically, density is defined as mass divided by volume:

### Some articles on density:

Density Estimation
... In probability and statistics, density estimation is the construction of an estimate, based on observed data, of an unobservable underlying probability density function ... The unobservable density function is thought of as the density according to which a large population is distributed the data are usually thought of as a random sample from that population ... A variety of approaches to density estimation are used, including Parzen windows and a range of data clustering techniques, including vector quantization ...
Spectral Density
... specific terms which are used are the power spectrum, spectral density, power spectral density, or energy spectral density ...
Density - Other Common Units
... The SI unit for density is kilograms per cubic metre (kg/m3) Litres and metric tons are not part of the SI, but are acceptable for use with it ... Liquid water has a density of about 1 kg/dm3, making any of these SI units numerically convenient to use as most solids and liquids have densities between 0.1 and 20 kg/dm3 ... tons) per cubic metre (Mg/m3) In US customary units density can be stated in Avoirdupois ounces per cubic inch (oz/cu in) Avoirdupois pounds per cubic inch (lb/cu ...
Boussinesq Approximation (buoyancy)
... It states that density differences are sufficiently small to be neglected, except where they appear in terms multiplied by g, the acceleration due to gravity ... the Boussinesq approximation is used since sound waves move via density variations ... arises because when considering a flow of, say, warm and cold water of density and one needs only consider a single density the difference is negligible ...
Classification By Schwarzschild Radius - Stellar Black Hole
... If one accumulates matter at nuclear density (the density of the nucleus of an atom, about 1018 kg/m3 neutron stars also reach this density), such an accumulation would fall within its own ...

### More definitions of "density":

• (noun): The amount per unit size.
Synonyms: denseness