Density (volumetric mass density or specific mass) is a substance's mass per unit of volume. The symbol most often used for density is ρ (the lower case...

Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans...

Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance...

is finite, one may compute the energy spectral density. More commonly used is the power spectral density (PSD, or simply power spectrum), which applies...

In probability theory, a probability density function (PDF), density function, or density of an absolutely continuous random variable, is a function whose...

This is a list of countries and dependencies ranked by population density, sorted by inhabitants per square kilometre or square mile. The list includes...

pixels per centimetre (ppcm or pixels/cm) are measurements of the pixel density of an electronic image device, such as a computer monitor or television...

Power density, defined as the amount of power (the time rate of energy transfer) per unit volume, is a critical parameter used across a spectrum of scientific...

In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy...

In quantum mechanics, a density matrix (or density operator) is a matrix that describes an ensemble of physical systems as quantum states (even if the...