The term for a female horse is "mare." A mare is typically an adult female horse, though young females may be referred to as fillies until they reach maturity, usually around three years of age. Mares are known for their nurturing behavior, often bonding closely with their foals. They are significant in equestrian activities, including riding, racing, and agriculture. Breeding programs often prioritize mares for their temperament, lineage, and performance, making them vital to the equine industry.