Mafi yawan ƙamus na ma'anar kalmar "BOD" ita ce gajarta ta "Biochemical Oxygen Demand." BOD yana nufin adadin narkar da iskar oxygen da ƙananan ƙwayoyin cuta ke cinyewa yayin da suke lalata kwayoyin halitta a cikin ruwa. Ana amfani da shi sau da yawa a matsayin ma'auni na matakin gurɓataccen ruwa a cikin ruwa, kamar yadda matakan BOD mafi girma ya nuna matsayi mafi girma na kwayoyin halitta don haka mafi girma matakan gurɓata. Ana auna BOD a cikin milligrams na iskar oxygen da ake cinye kowace lita na ruwa a kan takamaiman lokaci.