A free-ranging dog is any dog that is not contained. Free-ranging dogs include wild dogs, feral dogs, stray dogs, street dogs, and village dogs, as well as dogs allowed to come and go freely by their owners. The term is used when distinctions of ownership are irrelevant. It sometimes overlaps with the polysemic term pariah dog. The World Health Organization reports that there are 200 million stray dogs worldwide.
Ecologists find it important at times to distinguish between urban free-ranging dogs and rural free-ranging dogs. The distinction can be important as the ecological impact of and evolutionary pressures on these groups can be quite different.
Rural free-ranging dogs that rarely if ever leave a settlement are called village dogs. They are considered neither wild nor feral, and have less impact on the surrounding ecosystem than other rural free-ranging dogs. They pose a different set of environmental pressures than feral or wild dogs, or even free-ranging farm dogs. Experts on the behavior of early and primitive dogs have also noted interesting physical and behavioral differences between village dogs and other more feral free-ranging dogs. For example, village dogs tend to be smaller and occur more often alone or in pairs.
Village dogs include the African village dog and East Asian village dog, two types that were the earliest to be domesticated.
The term pariah dog has been used inconsistently, but is sometimes used synonymously, if incorrectly, with free-ranging dog. Originally, it referred to the landrace of free-ranging dogs native to India and other Asian countries. It later came to be used for primitive natural breeds of dogs of a similar physical appearance in other parts of the world. The United Kennel Club has a category of dogs called the "Sighthound & Pariah Group", which includes: primitive dogs; distinctive, local, free-ranging landraces; breeds recently developed from naturally selected populations; and very ancient breeds.