What is a newborn horse commonly referred to as?

A newborn horse is commonly referred to as a foal. This term specifically indicates a young horse under one year of age, regardless of its sex. It encompasses all newborn horses, whether they are male or female.

On the other hand, a colt refers specifically to a male horse that is typically under four years old. A filly denotes a female horse that is also young, usually under four years of age. The term pony is not related to age but rather describes a specific type of horse that is smaller in size and typically refers to horses that stand 14.2 hands (58 inches) or shorter at the withers. Each of these terms has specific definitions and uses within the equine vocabulary, which is why foal is the correct answer for a newborn horse.