Pigs are a genus of even-toed ungulates within the family Suidae. The name hog most commonly refers to the domestic pig (Sus domestica) in everyday parlance, but technically encompasses several distinct species, including the Wild Boar. Swine is a non-declensive noun generally used to describe a herd of pigs rather than an individual, however it may often be implied in a pejorative manner to any living being expressing pig-like behaviour. (Source Wikipedia)