ven/o, ven/i or phleb/o is a combining form that pertains to “vein”.
A vein is a blood vessel that carries deoxygenated blood from the tissues back to the heart. The pulmonary vein and umbilical vein, which carry oxygenated blood to the heart, are exceptions. Compared to arteries, veins are less muscular and are often located closer to the skin.