Learner's definition of DUAL
always used before a noun
1 : having two different parts, uses, etc.
the dual purpose of the study
The song's lyrics have a dual [=(more commonly) double] meaning.
a dual function
She held dual citizenship in France and the United States. [=she was a citizen of both countries]
2 : having two of something
Our car has dual air bags. [=has two air bags]
She pursued dual careers in music and acting.
families with dual incomes