A duplex is a residential building that contains two separate living units within one structure. These units can be arranged side-by-side, sharing a common wall, or stacked one above the other, each with its own entrance
. Typically, the two units are similar or mirror images in layout and size, and the building is owned by a single owner who may live in one unit and rent out the other
. The term "duplex" is distinct from other multi-unit buildings like triplexes or fourplexes, which have three or four units respectively
. In some places, such as parts of the U.S., Canada, and Australia, the term may also refer to slightly different configurations, but the core idea remains two attached homes in one building
. In urban areas like Manhattan or Chicago, a "duplex apartment" can mean a single unit spread over two floors connected by an internal staircase, rather than two separate units
. Overall, a duplex offers the advantage of having two separate residences under one roof, often making it an attractive option for homeowners who want to live in one unit and generate rental income from the other
