Nitrite is a salt or ester of nitrous acid, containing the anion NO2? or the group -NO2. Nitrites have the general formula RONO, where R is an aryl or alkyl group (in organic chemistry).
Nitrite is an intermediate in the process of nitrification (in the nitrogen cycle). Nitrite is a highly toxic substance that is produced by the oxidation of ammonia by Nitrosomonas bacteria. It is is almost immediately converted into nitrate.