狗又称“犬”，一种多用途家畜。中国古代将大者称犬，小者称狗，现多通用。犬是人类最早驯化的动物之一。作为家畜已有1万多年历史。最初供狩猎﹑放牧﹑守门﹑追踪和曳挽等役用。现今西方国家盛行养狗，已成为人的一种伴侣动物。医学上还作实验动物用。
警犬、猎犬、牧羊犬，都凭借了犬的优势——听觉、嗅觉极其灵敏，尖牙锐利，聪明机警，容易训练，又奔跑迅速。警犬帮助人侦察、搜捕、戒备案犯，猎犬帮助人追踪、捕获野物，牧羊犬帮助人守卫羊群，能发挥很大的作用。
犬的野生祖先很可能是广泛分布于欧亚及美洲大陆的狼，在其它地方也可能还有胡狼的血统。最初，体型较小的变种狼由于常到人的住处附近觅食，以及人逐渐知道可以利用它们来报警和协助狩猎等而发展了与人之间的相互依赖关系，又经过人的长期选择而产生了犬。现在犬的分布遍及全球，凡是有人居住的地方几乎都有犬存在。
You may have a dog for a pet at your house.Maybe you have some friends who have dogs.
No one knows how many millions of people in the world have dogs for pets.More than 1million new purebred dogs get registered (signed up)with the American Kennel Club (AKC)each year.The AKC is the main organization for purebred dogs in the United States.A purebred is a dog whose parents and ancestors all came from the same breed of dog.A dog of mixed breeds is sometimes called a mongrel or a mutt.
There are about 150different breeds，or kinds，of dogs.Each breed varies widely in appearance，size，intelligence，and behavior.For thousands of years，people have trained dogs to hunt for food，herd animals，and guard homes and farms.But most people just keep dogs as pets because they make friendly，loyal companions.
Terriers are one of the seven dog groups of the American Kennel Club.They were bred to hunt and catch small animals.This photograph shows a Cairn terrier.
The Alaskan Malamute is a working dog.Working dogs are one of the seven dog groups of the American Kennel Club.They are obedient and strong.
The border collie is a herding dog.Herding dogs are one of the seven dog groups of the American Kennel Club.Herding dogs were bred to keep farm animals from straying.
The golden retriever is a sporting dog.Sporting dogs are one of the seven dog groups of the American Kennel Club.Sporting dogs were bred to bring back ducks and other wild birds that hunters shoot.
Dogs need proper care.They need to have food and water，plenty of exercise，and grooming.Here，a poodle has its fur trimmed.
The Dalmatian is a medium sized，smooth coated breed of working and sporting heritage，suitable as a family pet or performance animal.He is an intelligent dog，devoted to his owners，and pleasant to live with.His most unique feature，his spots，are either black or chocolate brown.
What Are the Main Kinds of Dogs？
狗的主要种类
Beginning hundreds of years ago，breeders mated male and female dogs that had certain qualities，or traits.They wanted the puppies to have the same traits as the parents.Dogs that developed these traits were called breeds.
The AKC recognizes about 150breeds.It puts these breeds into seven groups called terrier，working，sporting，hound，herding，toy，and nonsporting dogs.
Terriers have stiff，wiry coats.Terriers were bred to hunt and catch foxes，badgers，and rabbits.
Working dogs are obedient and strong.The Alaskan Malamute is a working dog bred to pull sleds over ice and snow.
Sporting dogs，such as pointers and golden retrievers，were bred to bring back ducks and other wild birds that hunters shoot.Beagles and other hounds have a great sense of smell to help hunters track down rabbits and other small animals.
Collies，Welsh corgis，and other herding dogs were bred to keep farm animals from straying.Some toy dogs，such as Chihuahuas，were bred to be small companions for people.Nonsporting dogs are all the other breeds，from spotted dalmatians to curly haired poodles.
What Dogs Make the Best Pets？