These words denote types, ages and sexes of animals of the equine group, but especially of domestic horses of all sizes and breeds. Horse is the generic term. In its specific sense it refers to the full-grown, uncastrated male, or stallion , as contrasted with the full-grown female, or mare . Gelding refers to an adult male horse that has been castrated. When kept for breeding purposes, a stallion is often referred to as a stud horse . Mare refer to any female horse , but correctly to one at least four years of age that may be used for breeding.

A colt is any male horse , not gelded, under the age of four years. Filly is the term used of the female horse of the same age. Both these words denote race horses in the two-and three-year-old group.

A foal is a young colt or filly . The term is used until the animal is weaned: this normally takes place when the animal is five or six moths old. Foal is also the verb used when a mare gives birth.

Originally, a nag was a small horse used for riding, but the word now emphasizes an old; ill or broken-down animal. Nag is also used humorously of any horse .

Pony customarily refers to any of several breeds of very small horse , usually under 14 hands (about 56 inches) at the shoulder. Breeds such as the Shetland pony and the Welsh pony are usually ridden by small children or used to draw carts. The word is also a regional name in the American West for the horses that are used by cowboys while herding cattle or, in the past, for the horses ridden by Indians.

A cob is a short-legged, stocky little horse , of considerable strength, used either for riding or for pulling a light carriage.

A hunter is a horse that has been trained to carry a person of any weight, as in a fox hunt. He must have great endurance, since a hunter runs for long distances over rough terrain and has to be able to jump fences, streams etc., with ease.

Steed is a literary term for a spirited war horse or one ridden on occasions of state and display: a knight on his richly caparisoned steed ; Queen Elizabeth on a coal-back steed . As in the case of nag , steed may also be applied to any mount, especially one of dubious ancestry or ridiculous aspect: The peasant boy’s steed was a lop-eared old donkey with one eye.

Horse , colt and filly are sometimes used figuratively of human beings. Horse suggests clumsiness, lack of delicacy, and even gluttony: to stamp up the stairs like a horse ; to sweat like a horse ; to eat like a horse . Colt and its adjective coltish convey the awkward, fresh charm of the older child or young adolescent who is having difficulty in co-ordinating his rapidly growing limbs. When applied to a girl or young woman, filly emphasizes abundant energy and playfulness as contrasted with the sedateness of maturity: an old fool in his sixties trying to make dates with twenty-year-old fillies .