In its common modern meaning, a mule is the offspring of a male donkey and a female horse, which is classified as a kind of F1 hybrid. The reverse, the offspring of a male horse and a female donkey, is called a hinny. The donkey or ass, Equus asinus, is a member of the Equidae or horse family, and an odd-toed ungulate. While different species of the Equidae family can interbreed, offspring are almost always sterile. Nonetheless, horse/donkey hybrids are popular for their durability and vigor. Click here for more Mule Information and click here for more Donkey informatione.