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The Differences Between a Foal, Filly, and a Colt.

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Misusing horse terms is a pet peeve for many, and I am one of them. For example, people often incorrectly refer to any young horse as a colt. The same occurs with fillies and foals, but different words distinguish between males, females, full-grown/immature, or newborn horses.

Young horses are classified by their sex and age into foals, fillies, and colts. A filly is a female horse under four, and colts are male horses under four. A young horse that has not yet reached its first birthday is called a foal regardless of gender.

It is a common misconception that all baby horses are called colts, but you shouldn’t use “colt” when referring to female foals. There are special terms for young horses and their specific genders, one of these words being “colts.”

Picture of a foal in a meadow.

Terms used to describe young horses.

“Young horses” are typically defined as animals less than five years of age. These young horses have yet to fully develop a mature body, but after two years old, they possess the energy, strength, and curiosity to learn and train.

The five most common terms used to describe young horses are colt, filly, foal, yearling, and weanling.

ColtMaleFour Years and youngerNot castrated
FillyFemaleFour Years and younger
FoalEither sexLess than one-year-old
WeanlingEither sexTypically between 4-7 monthsStopped sucking milk
YearlingEither sexBetween 1 and 2 years old

The differences between a filly and a colt.

Horses have different names depending on their gender. A young female horse, four years old or younger, is called a “filly.” In contrast, young uncastrated male horses that haven’t reached their fifth birthday are called Colts.

A foal can be referred to as a filly foal or colt foal. The same is true for weanlings, you can call them weanling filly or weanling colt, and when it’s a yearling, it will be a yearling filly or colt.

Picture of a thoroughbred stallion.
Two-year-old colt

When you should use “colt” to describe a horse.

A male horse is referred to by various terms depending on its particular stage of life. When born, they are called foals or foal “colt.” I even hear people refer to young colts as stud colts.

Colt is the correct word to use for a young male horse under four, except if it’s been castrated, then the proper term to describe the horse is “gelding.” Male horses over four are called horses, stallions, or studs.

Picture of a racing form.

Colts in horse racing

In horse racing forms, a male racehorse between two and four years old is listed as a colt unless castrated; then, it is listed as a gelding. Once it reaches five, it is listed in the racing forms as a horse.

In the photo above, the horses are listed by color, gender, and age. Number 4 is a 5-year-old bay horse, and Number 5 is a 4 yr. old chestnut gelding.

Origin of the word “colt.”

The word “colt” to describe horses can be traced to Old English colt “a young horse,” also “young ass.,” In some Bible translations, it is also used for “young camel.”

There are many other possibilities for the etymology of the word colt. For example, “colt” could have derived from Proto-Germanic *kultaz or the Swedish word Kult meaning “young boar, piglet; boy,” to Danish’s use of kuld as a descriptor for young or inexperienced persons from early 13c.  

What does colt mean in slang?

While you can use the word colt to describe a young inexperienced male, it’s more commonly associated with describing an arrogant man that struts around.

Picture of a two year old filly.
Two-year-old filly

When you should use “filly” to describe a horse.

“Filly” is the word for young female horses; more specifically, it’s a female horse under five years old. When a filly reaches maturity at five, she will be called a mare. The horse above is a two-year-old filly named Olivia that we have in training.

Newborn females may be called filly foals, and as they age, weanling fillies and yearling fillies. These combinations provide their gender and stage in life. A yearling filly is a female horse that hasn’t reached her second birthday, and a weanling filly is a young female horse no longer suckling.

Origin of the word “filly.”

The word originates from the Old Norse fylja, which means “to follow.” It’s believed that it was originally used to describe an animal in its first year of life who would closely follow its mother as she grazed on the land and led other animals back into her care if they wandered off.

Picture of a three-year-old racing filly I recently bought.
Three-year-old filly

Fillies in horse racing

In racing forms, female horses four years old and younger are listed as fillies. Many races are restricted to fillies and mares. I recently bought a three-year-old filly named Mindy; she is running her second race this month; it is a maiden claiming restricted to fillies and mares; that’s her in the picture.

However, it’s not unusual for fillies to compete against their male counterparts and be successful. Some of the greatest racehorses were females, such as Ruffian and Winx, and a few even won the Kentucky Derby.

What does filly in slang mean?

The term “filly” dates back to the 18th century when it was used as a synonym for a mischievous child or young woman with quick wit and energy. Over time, this sense of the word has fallen out of usage due to its sexist implications.

However, if you’re looking for a word that still captures the characteristics of good-looking young women with quick wit fillies, work!

Picture of a chesnut baby horse.
Quarter horse weanling

Correct use of foal to describe a horse.

Foals are baby horses less than one year old. A foal becomes a yearling when it turns one. Male foals can be called colts, and females can be fillies. When a pregnant mare has her baby, you say she’s foaling.

Origin of the word “foal.”

The word “foal” comes from Old English, Fola meaning small or little. It is also related to other terms, such as Vulon in Dutch, which means baby or child.

Below is a cute YouTube video of a newborn foal taking its first steps.


What is a weanling?

A weanling is a baby horse that has been weaned from its mother. In other words, it’s a horse that recently stopped nursing and began eating solid food. A weanling can be any type of mammal but most commonly refers to young horses.

What is a yearling?

The yearling is a horse that is between the ages of one and two. The term “yearling” often refers to young horses who have been weaned from their mother’s milk, but it can also refer to any animal in its first year of life.