Duplex description can be different depending on the part of the US, but generally has two to four dwellings with a door for each and usually two front doors close together but separate—referred to as 'duplex', indicating the number of units, not the number of floors, as in some areas of the country they are often only one story. Groups of more than two units have corresponding names (Triplex, etc.). Those buildings that have a third storey are known as triplexes. See Three-decker (house)