carbon cycle

noun

1

: the cycle of carbon in the earth's ecosystems in which carbon dioxide is fixed by photosynthetic organisms to form organic nutrients and is ultimately restored to the inorganic state (as by respiration, protoplasmic decay, or combustion)

2

: a cycle of thermonuclear reactions in which four hydrogen atoms synthesize into a helium atom by the catalytic action of carbon with the release of nuclear energy and which is held to be the source of most of the energy radiated by the sun and stars

Examples of carbon cycle in a Sentence

Recent Examples on the Web

Possible causes include volcanic activity associated with the breakup of the supercontinent Pangaea, leading to climatic changes, ocean acidification and disruptions in the carbon cycle. —Scott Travers, Forbes, 7 Sep. 2024

Even the carbon cycle could be affected, as there will be fewer tiny life forms absorbing carbon dioxide. —Jude Coleman, Smithsonian Magazine, 6 Sep. 2024

This is the biggest methane sink, or source of loss, in Earth’s carbon cycle. —Lauren Leffer, Popular Science, 24 July 2024

Scientists and marine experts note the crucial role of whales in the ocean’s carbon cycle, acting as fertilizer pumps by consuming nutrients from the deep sea and releasing them at the surface through defecation. —Jared Formanek, CNN, 14 June 2024

Word History

First Known Use

1901, in the meaning defined at sense 1

Kids Definition

carbon cycle

noun

: the cycle of carbon in living things in which carbon dioxide is used in photosynthesis to form food and growth substances and is later returned to the environment by respiration, decay, and burning

Medical Definition

carbon cycle

noun

: the cycle of carbon in living beings in which carbon dioxide is fixed by photosynthesis to form organic nutrients and is ultimately restored to the inorganic state by respiration and protoplasmic decay