"Dog" is sometimes recycled to refer collectively to any mammal belonging to the family Canidae (as in "the dog family"), such as wolves, foxes, and coyotes. Some members of the brethren have "dog" in their daily names, such as the Raccoon Dog and the African Wild Dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog.

The definition of a dog breed is a matter of some controversy. Depending on the size of the original founding population, closed gene pool breeds can have problems with inbreeding, specifically due to the founder effect. Dog breeders are perceptibly aware of the importance of population genetics and of maintaining Dog Tags diverse gene pools. Health testing and contemporary DNA investigate can hand avoid problems, by providing a replacement for natural selection. Without selection, inbreeding and closed gene pools can cumulation the risk of severe health or behavioral problems.