A stray dog, mongrel, mutt or mixed-breed dog is a dog that does not belong to one officially recognized breed and including those that are the result of intentional breeding. Although the term mixed-breed dog is sometimes preferred, many mongrels have no known purebred ancestors (...)
Although mongrels are viewed as of less commercial value than
intentionally bred dogs, they are thought to be less susceptible to
genetic health problems associated with inbreeding (based on the
theory of heterosis), and have enthusiasts and defenders who prefer
them to intentionally bred dogs.