Population is the process of populating a geographic area, as by procreation or immigration.

In the most common sense of the word, the population of a geographic area is the number of people, or organisms of a particular species, who live in that area. Human population is studied by sociology and geography. Animal population is studied by biology and in particular, population biology[?], a branch of ecology, and population genetics.

In biology, a special sense of population is to denote a breeding group; which solely breeds amongst each other, though biologically could breed with all members of the species or subspecies. The reasons for doing so include physical isolation and behavioral differences.

A particular amount of land is said to have a carrying capacity, which limits population growth. Some observers of human societies have proposed that the concept of carrying capacity also applies to human population, and that unchecked population growth can result in a Malthusian catastrophe. Others vehemently oppose this view.