A female horse is called a filly while the male is called a stallion. Most horses are born at night and they can stand up within one hour after being born. A horse's height is calculated in hands and it belongs to the equus family.
A female horse over the age of four is called a mare
A female horse is referred to as a mare. When a female horse is young, they are known as a filly. Another interesting fact is that in the United Kingdom, a female donkey is referred to as a mare.