carbon cycle: Meaning and Definition of

car'bon cy"cle

1. the circulation of carbon atoms in the biosphere as a result of photosynthetic conversion of carbon dioxide into complex organic compounds by plants, which are consumed by other organisms: the carbon returns to the atmosphere in the form of carbon dioxide as a result of respiration, decay by fungi, bacteria, etc., and combustion of fossil fuels.
2. a cycle of nuclear transformations in the interiors of the stars by means of which hydrogen is gradually converted into helium with the release of nuclear energy.