The dog (Canis lupus familiaris) is a mammal from the family Canidae. It has been domesticated by humans for a long time. It was the first animal ever to be domesticated. Dogs are used by humans for many different things, for work and as pets. They are a popular pet because they are usually playful, friendly, and listen to humans. Thirty million dogs in the United States are registered as pets.[1] Dogs eat both meat and vegetables, often mixed together and sold in stores as dog food. Dogs often have jobs, including as police dogs, army dogs, seeing eye dogs, fire dogs, messenger dogs, hunting dogs and sheepdogs.
They are sometimes called "canines" from the Latin word for dog - canis. Sometimes people also use "dog" to describe other canids, such as wolves. A baby dog is called a pup or puppy. A dog is called a puppy until it is about one year old.
Dogs are sometimes referred to as "man's best friend" because they are kept as domestic pets and are usually loyal and like being around humans.