Hoofed, herbivorous mammal now represented by a single extant genus, Equus. The term horse commonly refers only to the domestic Equus caballus and to the wild Przewalski's horse. (Other so-called wild horses are feral domestic horses or their descendants.) Adapted to plains environments, all Equus species, including the ass and the zebra, have lengthened foot bones ending in a single toe covered by a hoof, for fast running; teeth shaped for grinding grass; and intestinal protozoa for digesting cellulose.

Small horse, officially any horse under 14.2 hands (58 in./145 cm) high. Most ponies are of Celtic origin. They are noted for their extreme hardiness and gentle natures. Some ponies are only 26 in. (65 cm) high. See Shetland pony; Welsh pony.

Found all over the world and come in various colors and coat patterns. The designation of miniature horse is determined by the height of the animal, which, depending on the particular registry involved, is usually less than 34-38 inches (82-91 cm) as measured at the withers.