lung

n. one of two saclike respiratory organs responsible for transferring oxygen into the bloodstream

For the village in Tibet, see Lung, TibetThe lung is the essential respiration organ in air-breathing vertebrates, the most primitive being the lungfish. Its principal function is to transport oxygen from the atmosphere into the bloodstream, and to excrete carbon dioxide from the bloodstream into the atmosphere. This exchange of gases is accomplished in the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli. The lungs also have non respiratory functions.
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Lung the organ of respiration ; either of the pair of organs that effect aeration of blood, lying on either side of the heart within the chest [more]Lung - Community and Resources

Noun
1. either of two saclike respiratory organs in the chest of vertebrates; serves to remove carbon dioxide and provide oxygen to the blood
(hypernym) respiratory organ
(part-holonym) lower respiratory tract
(part-meronym) bronchial artery

(n.)
An organ for aerial respiration; -- commonly in the plural.