There are about 400 kinds of purebred dogs. A purebred is a dog whose sire (father) and dam (mother) belong to the same breed and whose ancestors were purebred from the time the breed was recognized. In developing a breed, individual dogs that exhibit desired characteristics are mated. Mixed-breed dogs, also known as mutts or mongrels, have parents who belong to different breeds or who are of mixed breeding themselves.

Various organizations throughout the world keep records of dog breeding. In the United States, the best-known dog registry is the American Kennel Club (AKC). The Canadian Kennel Club in Canada and the Kennel Club of Britain have similar functions.

The AKC classifies dog breeds into seven major groups for exhibition in dog shows. The seven groups are: (1) sporting dogs, (2) hounds, (3) working dogs, (4) terriers, (5) toy dogs, (6) nonsporting dogs, and (7) herding dogs.

The AKC also has a miscellaneous category for dogs that are growing in popularity but that have not yet been accepted for registration. These breeds include the Australian kelpie and spinoni Italiani.


Sporting Dogs
Sporting dogs were developed to assist hunters who use guns. Breeds in this group are also called gundogs. They include pointers, setters, retrievers, and spaniels. Pointers and setters point their body toward hidden game. Retrievers pick up birds that have been shot and bring them back to the hunter. Most spaniels, including cocker and springer spaniels, flush birds from the brush.


Hounds
Members of this group are breeds that were developed to hunt. Some breeds in the group, including beagles, basset hounds, and bloodhounds, are called scent hounds because they hunt by scent. Others, such as greyhounds, salukis, and whippets, were bred to hunt game by sight and are known as gazehounds or sight hounds. Some hounds were developed to catch and kill the prey. Others corner the game and hold it at bay until the hunter arrives to kill it.


Working dogs
Members of this group vary greatly in size and in the purposes for which they were developed. Working dogs include breeds developed for guarding and hauling. Alaskan malamutes, Samoyeds, and Siberian huskies pull sleds. St. Bernards and Newfoundlands were bred for rescue work.


Terriers
Breeds included in this group were originally developed to dig into the earth to pursue prey. In the past, they specialized in hunting rodents and other small animals, such as badgers and rabbits. Some terriers were used for dogfighting before such contests were generally banned as cruel.


Toy dogs
Consisting of small breeds kept almost entirely as pets. Small varieties of poodles and Manchester terriers also compete in the toy group at dog shows. The largest toy dog is the pug, which may weigh up to 18 pounds (8 kilograms).


Nonsporting dogs
Members of this group are large companion dogs that may have originally been developed for work or sport. Poodles, for example, once retrieved ducks for French hunters, and bulldogs were bred for a sport called bull-baiting.


Herding dogs
Members of this group were classified in the working group until the AKC created a new group for herding breeds in 1983. All of these breeds were developed to keep sheep and cattle from straying and to protect livestock from predators. The herding group includes such popular pet breeds as the collie and the German shepherd dog.