The term "azygous vein" refers to a large vein that runs up the right side of the spinal column and carries deoxygenated blood from the lower limbs, back to the heart. There are several synonyms for this anatomical structure, including the azygos vein, azygous system, or simply the azygous. The azygous vein is a critical part of the circulatory system, and it is closely associated with other veins and arteries in the body. While there are variations in terminology used to describe this vein, the underlying anatomy remains the same, and it is essential for maintaining proper blood flow throughout the body.