Vena cava

n. (Medicine) either of two main veins that carry blood to the right atrium of the heart; superior vena cava or the inferior vena cava

The superior and inferior vena cava are collectively called the venae cavae. They are the veins that return de-oxygenated blood from the body into the heart. They both empty into the right atrium.The inferior vena cava (or posterior vena cava) travels up alongside the abdominal aorta with blood from the lower part of the body.The superior vena cava (or anterior) is above the heart, and forms from a convergence of the left and right brachiocephalic veins that contain blood from the head and the arms. The vena cavae carry deoxygenated blood from the body to the right atrium of the heart. The venae cavae is the largest blood vessel in the heart.
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Vena ca·va n. pl. venae ca·vae Either of the two venae cavae, designated inferior and superior. Also called cava. [more]Vena cava - Community and Resources

Noun
1. either of two large veins that return oxygen-depleted blood to the right atrium of the heart
(hypernym) vein, vena, venous blood vessel
(hyponym) inferior vena cava, postcava

The superior vena cava is the large vein which returns blood to the heart from the head, neck and both upper limbs. The inferior vena cava returns blood to the heart from the lower part of the body.