A large vein on the right side at the back of the thorax, draining into the superior vena cava.
- ‘A persistent left superior vena cava may be associated with the presence of two azygos veins.’
- ‘Other unusual sites of drainage include the coronary sinus, inferior vena cava, azygos vein, left subclavian vein, portal vein, and left persistent superior vena cava.’
- ‘The thoracic duct is located slightly ventral and medial to the azygos vein.’
- ‘The thoracic duct has also been found draining into the azygos vein and the inferior vena cava.’
- ‘When this occurs the posterior intercostal veins on the left side of the thorax may drain into the azygos vein independently.’
Mid 17th century: azygos from Greek azugos, from a- without + zugon yoke the vein not being one of a pair.