Meaning of DUAL in English

[adjective] [before noun; not gradable] - with two similar parts or combining two thingsThis room has a dual purpose, serving as both a study and a dining room.The dual role of chairman and chief executive is not unusual in the publishing business.A car with dual controls has two sets of controls such as brakes, one for the person who is learning to drive and one for the teacher.Someone with dual nationality/citizenship has the nationality of two countries at the same time.dual British and American nationality(UK) A dual carriageway (US and ANZ divided highway) is a road which has an area of land in the middle, dividing the rows of traffic which are moving in opposite directions.See picture: RoadsIf something is dual-purpose, it can be used to do two things.a dual-purpose lawn-raking and leaf-collecting machine.

Cambridge English vocab.      Кембриджский английский словарь.