Real Dictionary

carbon cycle in American English
the cycle by which plants through photosynthesis use atmospheric carbon dioxide to produce carbohydrates, which are in turn metabolized by animals to decomposition products that return carbon dioxide to the atmosphere
noun: 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

carbon cycle in British English
noun: the circulation of carbon between living organisms and their surroundings. Carbon dioxide from the atmosphere is synthesized by plants into plant tissue, which is ingested and metabolized by animals and converted to carbon dioxide again during respiration