A young female horse is called a filly, and a mare once she is an adult animal.
[3] The term is derived from Proto-Germanic *kultaz ("lump, bundle, offspring") and is etymologically related to "child.
In some cases, particularly informal nomenclature, a gelding under four years is still called a colt.
A rig or ridgling is a male equine with a retained testicle or one which has been incompletely castrated.
The terms "rag" or "rake" have been historically used to refer to a group of colts, but they have fallen out of modern usage.