What are all the names of horses stages of life?

Foal: a baby horse of either gender, normally under 6 months old. (Some people refer to a foal as a colt, no matter the gender although technically, a colt means a male foal)

Weanling: a young horse of either gender between 6 and 12 months old

Yearling: a horse between one and two years old of either gender.

Colt: A male horse less than 5 years old.

Filly: A female horse under 5 years old.

Mare: A female horse over 5.

Stallion: an un-castrated male horse over 5 years old.

Gelding: A castrated male horse of any age.

A stud is another Word used for stallion, although stud is actually a breeding stallion. Some colts are sometimes refered to as stud colts.