Horse, large land mammal notable for its speed, strength, and endurance. Horses are members of the Equidae family, which also includes zebras and asses. Like all equids, the horse is extremely well adapted to traveling long distances with great efficiency and to surviving on a diet of nutrient-poor, high-fiber grasses. The horse is an intensely social animal, forming strong associations with members of its herd and possessing a keen ability to recognize subtle social cues. These instinctive behaviors form the basis of the horse’s ability to bond with and obey a human trainer.