Ma'anar ƙamus na kalmar "wajibi" ita ce sanya wajibci ga wani ya yi wani abu, ko tilastawa ko ɗaure wani ga wani aiki. Hakanan yana iya nufin a buƙata ta aiki, doka, ko al'ada don yin wani abu. A ilmin halitta, "wajibi" yana nufin kwayoyin halitta da ke iya rayuwa kawai ko aiki ta wata hanya ta musamman, kamar kwayar cutar da ba ta iya rayuwa kawai ta rayuwa akan kwayoyin halitta.
