نریان

thumb|A stallion thumb|A stallion's secondary characteristics include heavier muscling than is seen in mares or geldings, often with muscular development along the crest of the neck. A stallion is an adult male horse that has not been gelded (castrated). Stallions follow the conformation and phenotype of their breed, but within that standard, the presence of hormones such as testosterone may give stallions a thicker, "cresty" neck, as well as a somewhat more muscular physique as compared to female horses, known as mares, and castrated males, called geldings.