Yearling (horse)

A yearling is a young horse either male or female that is between one and two years old.^[1] Yearlings are comparable in development to a very early adolescent and are not fully mature physically. While they may be in the earliest stages of sexual maturity, they are considered too young to be breeding stock.^[2]

Yearlings may be further defined by sex, using the term "colt" to describe any male horse under age four, and "filly" for any female under four.