n. Chem. a colourless tasteless odourless gaseous element that forms four-fifths of the atmosphere and is an essential constituent of proteins and nucleic acids. °Symb.: n. nitrogen cycle the interconversion of nitrogen and its compounds, usu. in the form of nitrates, in nature. nitrogen fixation a chemical process in which atmospheric nitrogen is assimilated into organic compounds in living organisms and hence into the nitrogen cycle. nitrogenous adj.
[ F nitrogène (as NITRO-, -GEN) ]