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

This part of the carbon cycle acts like a natural thermostat. —Morgan Underwood, The Conversation, 19 Nov. 2025

The two-part public event invites community members to explore the future of Florida’s coral reefs and the hidden role of deep-sea fish in regulating the planet’s carbon cycle. —Diana Udel, Miami Herald, 22 Oct. 2025

Recently, his group at Max Planck managed to run a one-kilometer model, one that included complex processes like carbon cycles and the effects of aerosols, that could simulate 90 days in 24 hours. —Zack Savitsky, Quanta Magazine, 15 Sep. 2025

The ship is the key research tool for understanding Antarctic ecology, the carbon cycle in the Southern Ocean and the rate at which ice shelves are retreating, melting and causing sea-level rise. —Evan Bush, NBC news, 1 Sep. 2025

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