The dog (Canis lupus familiaris) is a domesticated subspecies of the gray wolf, a mammal of the Canidae family of the order Carnivora. The term can also be used more generally to encompass any member of the biological family Canidae, the Genus Caninae (also called “true dogs”). When referring to Canis lupus familiaris, the term is used to specify both feral and pet varieties. The domestic dog has been one of the most widely kept working and companion animals in human history. There are estimated to be 400 million dogs in the world. Wikipedia