du ‧ al /ˈdjuː ə l $ ˈduːəl/ BrE AmE adjective [only before noun]
[ Date: 1600-1700 ; Language: Latin ; Origin: dualis , from duo 'two' ]
having two of something or two parts ⇨ single
The bridge has a dual role, carrying both road and rail.
a dual system of education
She has dual nationality, of Canada and Britain (=she is a citizen of Canada and Britain) .
—duality /djuˈæləti, djuˈælɪti $ du-/ noun [uncountable]