The exchange of chemicals between living and nonliving reservoirs in the Earth System.

Natural processes that recycle nutrients in various chemical forms from the nonliving environment to living organisms and then back to the nonliving environment. Examples are the carbon, oxygen, nitrogen, phosphorus, sulfur, and hydrologic cycles.

The cycle of elements through the biotic and abiotic environment.

The flow of a substance among different places, environmental compartments (e.g., atmosphere, water column, organisms), and chemical forms as a result of geological, chemical, and biological processes.

Slow movement of elements from the environment, through food webs, then back into the environment (e.g. carbon cycle).

The movement of chemical elements from organism to physical environment to organism in more or less circular pathways.

The manner in which the atoms of an element critical to life (such as carbon, nitrogen, or phosphorus) move from the bodies of living organisms to the physical environment and back again.

The cycle in which nitrogen, carbon, and other inorganic elements of the soil, atmosphere, etc. of a region are converted into the organic substances of animals and plants of the region and released back into the environment.

The transformation and transport of substances within and among the atmosphere, biosphere, hydrosphere, and lithosphere via biological, geological, and chemical processes that are often cyclical in nature.

In ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a chemical element or molecule moves through both biotic ("bio-") and abiotic ("geo-") compartments of an ecosystem. In effect, the element is recycled, although in some such cycles there may be places (called "sinks") where the element is accumulated or held for a long period of time.