A filly is a female horse younger than how many years of age?

A filly is defined as a female horse that is younger than three years of age. This terminology is commonly used in the equine industry to differentiate young female horses from their adult counterparts, which are referred to as mares once they reach three years old. Understanding this classification is important for breeding, training, and showing practices within the equine sector. It allows handlers and trainers to tailor their care, training programs, and nutritional needs according to the age and developmental stage of the horse.