Akwai 'yan ma'anoni daban-daban masu yuwuwa ga kalmar "nox," dangane da mahallin:A cikin ilmin sunadarai, NOx yana nufin rukuni na nitrogen oxides, gami da nitrogen monoxide. (NO) da nitrogen dioxide (NO2). Wadannan mahadi suna samuwa ne lokacin da nitrogen da oxygen ke amsawa a cikin matakan konewa mai zafi, kamar waɗanda ke faruwa a cikin injin mota ko wutar lantarki. A cikin tarihin Roman, Nox (kuma an rubuta Nyx) ita ce allahn dare. Yawanci ana kwatanta ta a matsayin duhu, siffar inuwa mai fuka-fuki, kuma tana da alaƙa da asirai, duhu, da waɗanda ba a sani ba. dare."Ba tare da ƙarin mahallin ba, yana da wuya a tantance wanne daga cikin waɗannan ma'anoni (idan akwai) ya fi dacewa da tambayarka.