In thoroughbredhorse-racing, a filly is defined as a female horse less than five years old; in harness racing a filly is a female horse less than four years old. The male equivalent to a filly is a colt. An older female horse is called a mare.
It's fillies only for the co-feature, the $125,000 Torrey Pines at a mile on the dirt.
Juveniles are on the Monmouth Sunday bill in the Grade-3 Sapling Stakes at six panels for $150,000; and young fillies take on the same distance in the $100,000 Sorority Stakes.
Also at Saratoga, three-year-old-and-up fillies and mares in the Grade-3 category, go almost a mile and a half on the grass for $100,000 in the Glens Falls Handicap.
A filly is a female horse, specifically one which has not reached sexual maturity.
In Thoroughbred horse racing, the definitions of "filly" and "mare" are slightly different.
In this context, female horses are not classified as "mares" until they are five-year-olds—more precisely, on the fifth January 1 (for horses born in the Northern Hemisphere) or August 1 (for horses born in the Southern Hemisphere) after their actual date of birth.