Horses and ponies
Usually, size alone marks the difference between horses and ponies. The threshold is 14.2 hh (4 feet 10 inches, 1.47 m) for an adult. When a horse is 14.2 hh exactly, it is called borderline and is either a horse or a pony depending on the breed. Below the threshold an animal is a pony, while above the threshold it is a horse. Thus normal variations can mean that a horse stallion and horse mare can become the parents of an adult pony. However, a distinct set of characteristic pony traits, developed in northwest Europe and further evolved in the British Isles, make it less clear whether it is more appropriate to use the word "pony" to describe a size or a type. Many people consider the Shetland pony as the archetypal pony, as its proportions are so different from those of horses. Several small breeds are mostly referred to as "horses" but occasionally as "ponies", though that is generally considered improper by those familiar with the breeds. These include the Icelandic horse, Fjord horse and Caspian horse breeds. Breeders of miniature horses favour that name because they strive to reproduce horse-like attributes in a much smaller animal, even though their horses undeniably descend from horses of small stature, which are thereby classifiable as ponies by size.