the.com/nitrogen cycle

means The natural process by which nitrogen moves between the atmosphere, soil, and living things—fixed into usable forms, passed through organisms, and eventually released back into the air.

from 'Nitrogen' comes from French 'nitrogène,' coined in the late 18th century from 'nitre' (the saltpeter mineral, potassium nitrate) plus the Greek-derived suffix '-gen,' meaning 'producer of'—so literally 'nitre-maker,' since the gas was first characterized as the component of air that formed nitre compounds. 'Cycle' traces back to Greek 'kyklos,' meaning 'circle' or 'wheel.' The phrase itself emerged in the 19th century as chemists and early soil scientists mapped out how this once-inert-seeming gas actually loops endlessly through fixation, decay, and release—a circuit discovered only once microbiology revealed the bacteria quietly running the machinery.