(mathematics) The vector space which comprises the set of linear functionals of a given vector space.

(politics) A situation in which a person has been elected to two different bodies with different competencies, for example being a member of both a national legislature, and of a local authority.

Of media, giving the option to listen to audio in two different languages.

(category theory) For a given category C, its dual category Cᵒᵖ is obtained by reversing the direction of each one of the arrows of C.

Having two purposes; able to be used for two separate things.

(US, politics) Two primaries held concurrently.

Alternative spelling of dual-boot

(computing) Having two operating systems available, such that either of them can be selected each time the computer is booted.

capable of operating on two frequency ranges

plural of dual citizenship