withers
The highest part of a horse’s back at the neck.
The withers are the highest part of a horse's back, located between the shoulder blades at the base of the neck. If you've ever seen someone measure a horse's height, they measure to the withers, not the top of the head (since horses move their heads up and down constantly). A horse that measures 15 hands at the withers stands about five feet tall at that spot.
The withers matter for practical reasons. This bony ridge is where the horse's neck muscles and shoulder bones come together, creating a stable place for a saddle to rest. A saddle that fits poorly can rub against the withers and cause pain, making the horse uncomfortable or even injuring it. That's why riders check carefully that the saddle sits just behind the withers without pressing on them.
Some horse breeds have prominent, clearly defined withers, while others have flatter backs. Draft horses, built for pulling heavy loads, often have less prominent withers, while horses bred for riding usually have withers that help keep the saddle in place. Understanding where the withers are helps anyone working with horses fit equipment properly and keep the animal comfortable.