Gariiradda birta, sidoo kale loo yaqaan birta gariiradda. Birtu waa mid kulul oo qabow lagu riixay duubis. Si loo fududeeyo kaydinta iyo gaadiidka, way ku habboon tahay in la sameeyo farsamayn kala duwan (sida samaynta taarikada birta, birta, iwm. socodka, oo waxaa lagu rogrogaa fiilooyinka birta ee gariiriyaha. Gariiradaha, gariiradda xariijimaha birta la qaboojiyey, iyadoo loo eegayo baahiyaha kala duwan ee isticmaalayaasha, iyada oo loo marayo khadadka dhamaystirka ee kala duwan (heeraynta, toosinta, gooynta ama goynta, kormeerka, miisaamidda, baakadaha iyo calaamadaynta, iwm.