Population density (in agriculture : standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and particularly to humans. It is a key geographic term. Lists of population density of different countries are below. Lists of ot...
(from the article `population ecology`) Population density and growth[5 related articles]
The number of cats (organisms) of a population per unit area of a particular territory.
<epidemiology> Number of individuals in a population relative to space. ... (12 Dec 1998) ... 
Number of individuals of a species per unit of area.
The number of persons who inhabit a unit area (usually per square mile).
The number of people in a certain area.The number of individuals of one population per unit area or volume.the concentration of people within a specific portion of a defined area
Number of individuals of a particular species found in a specified area.
The number of individuals per unit area in a given population.
Number of individuals per unit area or volume 
The number of people living in a given area, usually expressed as people per square kilometre. It is calculated by dividing the population of a region by its area. Population density provides a useful means for comparing population distribution. Densities vary considerably over the globe. High population densities may amount to overpopulation where...
The number of individuals of a species in an environment divided by the total land area, or water volume, of that environment. Population density is analogous to the concept of concentration in chemistry. In fact, population density is simply the concentration of organisms in a given area. Take that, Chemistry.