What does filly mean?
A filly is a young female horse, one that has not yet reached adulthood — typically a female under about four years old. Once mature, she is referred to simply as a mare. The term is standard, precise vocabulary within equestrianism, breeding, and horse racing, where it appears constantly in race cards, form guides, and commentary ('a talented three-year-old filly'). Its male counterpart is the colt, and together with the gender-neutral 'foal' these terms map out the early life stages of horses. Beyond its literal sense, 'filly' has occasionally been used figuratively for a lively or high-spirited young woman, though this usage now reads as dated and somewhat patronising. The word carries connotations of youthfulness, energy, and promise — a filly is often spoken of in terms of potential, particularly at the start of a racing career. Its distinctive sound and clear meaning make it a useful addition to any animal- or sports-related vocabulary.
nounA young female horse, especially one that has not yet reached full maturity (typically under about four years old).
- A young female horse, typically under four years of age, especially before it has been bred.
- (Figurative, informal) A lively, spirited girl or young woman — now largely dated and often considered patronising.
"The chestnut filly thundered down the final stretch to win her first race."
"The trainer decided the filly wasn't ready for the demanding three-mile course."
"In the paddock, a gangly brown filly nuzzled her mother for the first time."
Standard plural; the '-y' changes to '-ies' as with other nouns ending in consonant + y.
"The field of twelve fillies broke cleanly from the starting gate."
Every winner of the Epsom Derby from 1779 until today owes its name-check to the fact that 'Derby' was named after a earl whose race inspired a female-only counterpart called — naturally — The Oaks, where only fillies may run.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of filly
'Filly' derives ultimately from the Old English 'fula' meaning foal, which shares a common Germanic root with Old Norse 'foli' and modern German 'Fohlen' — all words for a young horse. It entered Middle English as a diminutive or affectionate variant of 'foal', gradually narrowing to mean specifically a young female horse. Its earliest attested uses date to around the fifteenth century, and it has been a fixture of English equine vocabulary ever since.
Related word forms
How filly is actually used
In horsemanship and racing contexts, 'filly' is precise terminology referring strictly to a female horse under roughly four or five years old; after maturity she is simply called a mare. The figurative use for a spirited girl is dated and can sound condescending today. In British horse-racing coverage, 'filly' is ubiquitous in race descriptions and form guides.
Easily confused with filly
"Philly" is an informal name for the city of Philadelphia (or a person named Philippa), while "filly" is a young female horse.
A colt is a young male horse, whereas a filly is a young female horse.