The terminology used for horses depends on their age and certain factors. Here is a breakdown:

A baby horse is known as a foal.

A male foal is called a colt.

A female foal is referred to as a filly.

A horse of either sex that is less than a year old and has been weaned is called a weanling. If it is still nursing, it is called a suckling.

Once a horse reaches the age of one year, it is called a yearling.

A male horse that has been castrated is called a gelding, regardless of its age.

If a male horse has one or both testicles undescended, it is known as a ridgling or rig.

An intact male horse is called a colt until it reaches the age of four or five, depending on the breed. After that, it is called a horse. Some people may refer to adult intact males as stallions, but this term specifically implies that the horse is used for breeding.

A male horse of any age that has been used for breeding is called a stallion.

A female horse is called a filly until it reaches the age of four or five, depending on the breed. Once it reaches that age, it is referred to as a mare. If the female horse has been bred, it is considered a mare regardless of its age.