Races for 3 year old thoroughbreds are restricted by entry conditions "for 3 year olds". The Triple Crown (Kentucky Derby, Preakness, and Belmont) are the most commonly known races for 3 year olds.
Thoroughbreds have to be a minimum of two years old to race. All races have their own age requirements. There are races for two-year-olds, three-year-olds (which are the more widely known ones like the Kentucky Derby, Preakness, and Belmont), three-year-olds and up, and four-year-olds and up.
the races for three year old in flat racing are referred to as a derby
Nursery
Yes. The Triple Crown races are for three year olds only.
No. Only three year old thoroughbreds can enter the derby, so they can only enter once.
Nursery
Nursery
Yes. They can be three years old only.
The ancestry of the modern thoroughbred traces back to three main sires. The Darley Arabian, the Godolphin Arabian, and the Byerly Turk.
They are raced at three years old because that is when they are full grown and are almost adults.
The Triple Crown, or respectively the Kentucky Derby, The Preakness, and The Belmont Stakes, are exclusively for three-year-old Thoroughbreds. Because the distance increases with each race it is harder for the horse to complete The Triple Crown. Last winner was 'Affirmed' in 1978, he was euthanized at the age of twenty six after an injury to his pastern caused him to suffer from laminitis. And actually, most of the horses that have run these races live well into their teens and many lived well into their thirties.
Race for "three year-olds". However, Thoroughbreds that are born in the Northern Hemisphere technically become a year older on January 1 each year and those born in the Southern Hemisphere turn one year older on August 1.