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

The new probe will allow scientists to understand exactly how carbon levels are fluctuating, teach scientists more about the carbon cycle and map areas of deforestation. —Sara Hashemi, Smithsonian Magazine, 11 Apr. 2025

Whales in turn play a role in the marine carbon cycle, sequestering CO2 in their gargantuan bodies while pooping in such great quantities as to stimulate the growth of other carbon-consuming organisms. —Bloomberg, The Mercury News, 18 Mar. 2025

Convincing financial markets of the value of carbon credits could protect forested ecosystems, which are vital to our planet’s carbon cycle and contribute so much to the variety and wonder of life on this lonely blue rock. —Erik Kobayashi-Solomon, Forbes.com, 3 Apr. 2025

This year’s report includes a detailed accounting of how the carbon cycle is changing in the Arctic. —Evan Bush, NBC News, 10 Dec. 2024

Word History

First Known Use

1901, in the meaning defined at sense 1

Rhymes for carbon cycle

• recycle
• motorcycle

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