The carbon cycle is that part of the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycle. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone. The carbon cycle comprises a sequence of events that are key to making Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration (storage) to and release from carbon sinks.

కర్బన వలయం లేదా కార్బన్‌ సైకిల్‌ లేదా కర్బన ఆవృతం అంటే వాతావరణంలోని కార్బన్‌ డయాక్సైడులోని కర్బనము‌ ప్రాణులలోకి ప్రవేశించి, తిరిగి వాతావరణంలోకి విడుదల కావడం.